Browsing Masters Degrees (Clinical Pharmacology) by Title
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- ItemAccuracy Optimization of anti-TB Drug Assays using Protein Evaluation in Calibration Curves during Pharmacokinetics Quality Assurance(Stellenbosch : Stellenbosch University, 2021-12) Vallie, Sarfaraaz; Stander, Marietjie; Reuter, Helmuth; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. Medicine: Clinical Pharmacology.ENGLISH ABSTRACT: Quality assurance of drug assaying is an important aspect in clinical testing. Accuracy is important to ensure correct bio-analytical results by constructing calibration curves that took blood matrix interferences into consideration. I have adhered to the United States of America Food and Drug Administration (FDA) call for improved accuracy in bio-equivalence, bio-availability and administering of narrow therapeutic indexed drugs. Significant different plasma levels were observed in clinical trials for the occasional hyperproteinemia (an increase in protein concentration in the bloodstream) and hypoproteinemia (lower-than normal levels of protein in the blood) patients this includes disease-related hyperalbuminemia (an increased concentration of albumin in the blood) and hypoalbuminemia (a deficit of albumin in the blood) patients. This research supported a modeled approach for accuracy improvements by including the patients‘ plasma protein levels using a combined calibration curve (protein evaluation calibrations curves – PROTECC-PKTM). Levels of albumin were classified as marked hypoalbuminemia (<2.5 g/dL), mild hypoalbuminemia (2.5-3.5 g/dL), normal albumin (3.5-4.5 g/dL), and hyperalbuminemia (>4.5 g/dL). This research was specifically important for drugs with a narrow therapeutic index. The rifampicin method was developed, validated and the concentration calibration curve of rifampicin with and without plasma was assessed. The limit of detection for rifampicin with and without plasma was 0.189 μg/ml ± 0.082 and 0.080 μg/ml ± 0.053 μg/ml respectively (LOD ± mean standard diviation). The limit of quantification of rifampicin with and without plasma was 0.573 μg/ml ± 0.082μg/ml and 0.243 μg/ml ± 0.053μg/ml respectively (LOQ ± mean standard diviation). The r2 for rifampicin was 0.9971 without plasma and 0.9852 with plasma present. A novel analytical method for determination of the % protein content present in blood plasma was performed using the Karl Fischer Titration process. Results indicated deviation in % protein of blood plasma for patients compared to literature values of about 8 %. Using the data obtained, the PROTECC-PKTM curves indicated that the relative accuracy differed by a minimum of 0.1% for low binding affinity drugs and a maximum of more than 20% for drugs with moderate binding affinities. The relative accuracy of the anti TB drugs was supported by computational modelling and thermodynamic analytical methods for each drug during multiple drug co-administration regimens. This study focused on the drug binding affinity that affects the extrapolation of the patient‘s sample drug concentration from the slope of LCMS calibration curve. The binding constants calculated from fluorescence spectroscopy data were as follows: rifampicin 5.379 x 102 M-1 (moderate affinity), isoniazid 9.285 M-1 (low affinity), 25-desacetyl rifampicin 3.156 M-1 (low affinity), ethambutol 3.443 M-1 (low affinity) and pyrazinamide 3.076 X 102 M-1 (moderate affinity). These drugs Gibbs free energies for these drugs indicated spontaneous binding reactions. Rifampicin, a non-polar weak acid with a higher affinity, showed the most stable complex formation with human serum albumin (HSA) compared to soluble isoniazid. This is because isoniazid in its ionized form can be easily excreted in the urine resulting in low levels of detection. This will affect the bioavailability and accuracy of the assay levels for patients experiencing hyper and hypoalbuminemia with related competition and induction processes of the enzymes. These complications are apparent where a larger number of patients are involved in clinical trials, bioequivalence and bioavailability studies with varying protein levels that may be more crucial for drugs with a narrow therapeutic index.
- ItemAcute poisonings : a comparative study of hospital admissions versus poison centre consultations(Stellenbosch : Stellenbosch University, 2001-12) Marks, C. J.; Muller, G. J.; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medicine. Division of Pharmacology.ENGLISH ABSTRACT: A prospective study was conducted in 1999 to establish the incidence and nature of acute poisonings in the Cape Town / Western Cape region. This study was based on an analysis of Poison Centre queries and acute poisoning admissions to Tygerberg Hospital over a period of 1 year (1999). Summary of findings for Hospital admissions (1010 cases): Acute poisonings were more common in adults (83%) than in children (17%) and drug overdose was by far the most common clinical entity in adult Hospital admissions (89% of cases). Most overdoses in adults were intentional (97%). Seventy five percent of these cases were female, predominantly in the 20-40 year age group. The incidence of non-drug chemical exposures in adults was relatively low (11%). In children, on the other hand, there was much less of a discrepancy between drug and non-drug chemical exposures (41% and 59% respectively). Paracetamol was the drug most commonly used in overdose in both adults and children. In adults ethanol featured in 17% of cases. Ingestion of paraffin and related volatile hydrocarbons were the most important cause of acute poisoning in children. Acute poisoning admissions due to drugs of abuse, excluding ethanol, were minimal in both age groups (1%). Toxic exposures to non-drug chemicals in the agricultural and industrial settings were low (3%). The number of exposures to biological toxins was also minimal (2%). Summary of findings for Poison Centre inqueries (3744 consultations): In 1999 the Tygerberg Poison Information Centre received 3744 calls, of which 2690 were related to acute human exposures to poisonous substances. The remainder of the calls (1054) was either about drug therapy, or general non-patient related toxicological matters. There were more calls regarding poisoning in adults (61%) than in children (39%). Most of the paediatric poisonings were accidental (97%), whereas in adults 55% were deliberate and 45% accidental. Forty four percent of the children and 52% of adults were female. In children, inqueries about exposures to potentially harmful non-drug household chemical products comprised 56% of poison calls, while drug overdose was 28% and exposures to biological toxins 16%. In adults 44% of inqueries were with regard to household products, 40% about drugs and 16% biological toxins. A comparison of Hospital admissions versus Poison Centre consultations: In order to make a valid comparison between Hospital admissions and Poison Centre consultations, acute poisoning cases originating from the same area were compared. Eight hundred and thirty four (90%) of patients admitted to Tygerberg Hospital and 592 (25%) of Poison Centre consultations originated from the same region, the Tygerberg catchment area. Several differences were noted when comparing poisoning cases reported to the Poison Centre and Hospital admissions. Six hundred and eighty eight (83%) adults and 145 (17%) children were admitted to Hospital in contrast to Poison Centre inqueries, where 322 (54%) were adults and 270 (46%) children. In adults, 99% of Hospital admissions versus 59% of Poison Centre consultations were regarded as self-inflicted. Ninety three percent of adults admitted to Hospital were drug overdoses, whereas only 48% of adult Poison Centre consultations involved ingestion of medicines. In adult overdoses with paracetamol and other analgesics, tricyclic antidepressants, antiepileptics, theophylline and ethanol were significantly higher in Hospital admissions than in Poison Centre consultations. In contrast, exposures to pesticides e.g. pyrethroids, misuse of recreational drugs e.g. cannabis and biological toxin exposures e.g. spider bites, were significantly higher in Poison Centre consultations than in Hospital admissions. In children, poisoning exposures to volatile hydrocarbons, especially paraffin, were significantly higher in Hospital admissions compared to Poison Centre enqueries. As is evident from the disparity in the results above, inqueries to the Tygerberg Poison Information Centre cannot be regarded as a reflection of the true incidence of acute poisonings in the community. Poison Information Centre statistics are distorted because of two factors: 1. Under-reporting to the Poison Information Centre. Healthcare providers are familiar with how to manage drugs commonly used in overdose (e.g. paracetamol) and certain household non-drug chemicals (e.g. paraffin), and often do not consult the Poison Centre for poison cases involving these substances. The number of inqueries received by the Poison Information Centre regarding these substances is, therefore, an under representation of actual incidence. 2. Over-reporting to the Poison Information Centre. The Tygerberg Poison Information Centre is well known for its expertise in biological toxins (e.g. spider and snake bites, scorpion stings, plant and mushroom ingestions, and marine toxins). Therefore, the number of inqueries received by the Centre with regard to these exposures is far higher than actual incidence of exposures. It is clear from this study that one cannot use data derived from a poison centre alone as an indicator of true incidence of poisoning in the community. A more accurate estimate of incidence of acute poisoning could be obtained by including data from hospital admissions, as well as those from primary health care facilities. Another prominent finding in this study was the high incidence of self-inflicted drug overdose in adult females, with paracetamol being the drug of choice. Poison prevention should therefore not be limited to children. Adult prevention programs need urgent attention.
- ItemAdverse drug reactions in paediatric in-patients in a South African tertiary hospital(Stellenbosch : Stellenbosch University, 2017-12) Makiwane, Memela MacDonald; Decloedt, Eric; Rosenkranz, Bernd; Kruger, Mariana; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medicine: Clinical Pharmacology.ENGLISH SUMMARY: Purpose: Paediatric patients have more adverse drug reaction (ADR) rates than adults due to off-label use of medicines and the prevalence data of ADRs in Sub-Saharan African children is limited. The aim was to describe the prevalence and nature of ADRs in paediatric (≤ 16 years old) in-patients at a tertiary hospital in South Africa. Methods: We conducted a prospective study of paediatric in-patients to identify suspected ADRs. Children had to be admitted for at least 24 hours during the 3-month study period (1 December 2015 to 29 February 2016). The data collected included age, sex, diagnosis and medicines received. We assessed causality using the 10-question Naranjo probability scale and classified severity using the Hartwig severity scale. Results: We found that 18.4% (52/282) of patients had 61 ADRs. The median age of patients with ADRs was 1.4 years (interquartile range (IQR): 0.5 – 5.3 years). ADR was the reason for admission in a third of the patients (31%; 16/52). Paediatric oncology patients suffered the majority of the ADRs (56.5%; 13/23), followed by HIV-infected patients on antiretroviral therapy (ART) (42.9%; 9/21) and tuberculosis (TB) patients (17.5%; 7/40). HIV-TB coinfected patients also experienced a high 30.8% (4/13) rate of ADRs. The majority of the ADRs were moderate 45.9% (28/61), while 42.6% (26/61) were mild, and 11.5% severe ADRs (7/61). These ADRs range from severe neutropaenia 4.9% (3/61) and drug induced liver injury (DILI) 4.9% (3/61) to mild cutaneous rashes 13.1% (8/61). There were no fatal ADRs, while 13.1% (8/61) ADRs were considered life threatening; 27.9% (17/61) necessitated and/or prolonged hospitalisation and 31.1% (19/61) resulted in persistent or significant disability or incapacity. Thirty eight percent of ADRs (23/61) were predictable. Paediatric oncology patients on chemotherapy were 7 times more likely to have ADR(s) than other patient groups [OR 7.3 (3.0 – 17.9), p < 0.01]. More ADRs were associated with chemotherapy 44.3% (27/61) and antimicrobials 42.6% (26/61), while the other miscellaneous medicine classes were associated with 34.4% (21/61) of the recorded ADRs. Conclusion: The prevalence of ADRs was 18.4% and in 31% the ADR was the reason for admission. The ADRs in paediatric oncology patients were expected, but of note nearly half the HIV-infected patients (43%) suffered an ADR.
- ItemAn analytical investigation of the impact of crushing of first-line antituberculosis medication and administration via a nasogastric tube(Stellenbosch : Stellenbosch University, 2022-11) Phogole, Cassius; Kellermann, Tracy; Faculty of Medicine and Health Sciences. Dept. of Medicine. Division of Clinical Pharmacology.ENGLISH ABSTRACT: Background Currently, the treatment of TB patients admitted to an intensive care unit (ICU) in South African Hospitals is performed by the off-label practice of crushing the first-line antituberculosis drugs isoniazid (INH), rifampicin (RIF), pyrazinamide (PZA) and ethambutol (EMB) and administration to the patients through a nasogastric (NG) tube as the majority of these patients are often sedated or intubated and therefore cannot swallow the whole tablets. This has, however, been associated with low drug exposure insufficient to effectively treat the Mycobacterial infection. Additionally, there is a paucity of alternative intravenous (IV) formulations of first-line antituberculosis drugs, especially in developing countries. The stability and solubility of these crushed drugs dissolved in water are questionable. Furthermore, the impact of the removal of the protective outer tablet coating and its effect on absorption and subsequent bioavailability has not been elucidated in the literature. Moreover, drug loss of crushed first-line antituberculosis drugs by adsorption to the surface materials used during medication preparation and administration via NG tube has also not been documented. Therefore, the present study aimed to investigate the root cause of the poor plasma drug exposure observed when crushing the first-line antituberculosis drugs and administration through an NG tube using laboratory-based techniques with possible translational interventions that can be applied in clinical settings to ameliorate their bioavailability. Methods The aqueous solubility of crushed drugs under the inversion mixing method was evaluated against easily implementable mixing methods (sonication and vortexing) with/without ascorbic acid (Asc). Moreover, the aqueous stability assessment of these crushed first-line antituberculosis drugs in mono-suspensions with/without Asc and co-suspensions at room and low temperatures was executed as well. The stability of the whole/crushed tablets in fasted-state simulated gastrointestinal fluids (FSSGIFs) was evaluated with/without Asc. Lastly, the drug loss by adsorption to the surface materials used during medication preparation and in vitro administration through an NG tube was quantitatively determined. Results Rifampicin (RIF) was the only drug showing poor aqueous solubility and instability in the simulated-gastric fluid. However, the addition of Asc has been shown to significantly (P<0.001) improve RIF solubility in both water and FSSGIFs with no detrimental effects. A minimum recommended volume of water (10 ml) to rinse the NG tube after administration of medication was shown to be inadequate to clear off all the residues of crushed antituberculosis medication. However, when an additional rinsing step with another 10 mL of water (total volume of 20 mL) was employed in the current study the amount of APIs of crushed first-line antituberculosis drugs adsorbed to these surface materials was significantly (p<0.001) reduced. Conclusion Co-administration of first-line antituberculosis medication with Asc when off-label crushing practice is used may improve RIF bioavailability. Furthermore, rinsing the NG tube with 20 mL of water after administering TB medication was shown to ensure adequate drug delivery, which may improve the bioavailability of nonpolar drugs that adhere to the surface of an NG tube.
- ItemAntimycobacterial agents : a study of Liposomal-Encapsulation, comparitive permeability of bronchial tissue and in vitro activity against mycobacterium tuberculosis isolates(Stellenbosch : Stellenbosch University, 2012-12) Van Rensburg, Lyne; Van Zyl, J. M.; Seifart, H. I.; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medicine. Pharmacology.ENGLISH ABSTRACT: In this thesis, research results are reported on the role of dipalmitoyl phosphatidyl choline (DPPC) and DPPC-liposomes on the in vitro permeability characteristics of various antimycobacterial drugs across porcine bronchial tissue. The permeability flux values of the different compounds (isoniazid, ofloxacin and moxifloxacin) and their relevant DPPC formulations were determined using a continuous flow through perfusion system. Mean steady state flux values were compared statistically by means of a t-test at a significance level of 5% as well as an F-test using whole curve comparisons. The results indicated that the different formulations of drug and their DPPC combinations retard the permeation of drug through bronchial tissue. However, moxifloxacin permeation was significantly enhanced when in a DPPC-liposomal formulation. These results demonstrate the important role that molecular weight, electrostatic charge, partitioning of the molecules in DPPC and DPPC-liposomes play in transmembrane diffusion. In addition, the effect of individual drugs and their DPPC combinations on the surface tension lowering property of DPPC was evaluated. The results obtained showed minimal decreases in the surface tension lowering capability of DPPC; however, the minimal increases in surface tension do not alter the integrity of DPPC to a large extent. Drug susceptibility testing of Mycobacterium tuberculosis cultures against the individual antitubercular drugs and their DPPC combinations was done by using the Radiometric BACTEC 460TB™ system. Drug-entrapped DPPC liposomes were tested at concentrations comparable to their relative minimum inhibitory concentrations (MIC). The results for the BACTEC assay indicated that the mycobacteria were susceptible to the developed drug entrapped liposomes; of which their encapsulation efficiencies for the relevant drugs were approximately ± 50%. It was concluded that drug-entrapped DPPC liposomes could fulfill the dual role of pulmonary drug delivery and alveolar stabilization due to antiatelectatic effect of DPPC which can improve the distribution of anti-tubercular drugs in the lung
- ItemBiophysical properties of experimental compositions of a synthetic pulmonary surfactant synsurf® for aerosolisation(Stellenbosch : Stellenbosch University, 2018-03) Agenbag, Chris-Mare; Van Zyl, Johann Martin; Smith, Johan; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medicine: Clinical Pharmacology.ENGLISH ABSTRACT: Synthetic pulmonary surfactant consists of phospholipid mixtures, free fatty acids and/or sterols, as well as specific protein constructs that mimic the functions of surfactant associated proteins B and/or C. Treatment of neonatal respiratory distress syndrome with surfactant replacement therapy consists of an invasive technique of endotracheal intubation and administration into the airway. For this reason, a less invasive approach such as nebulisation in these frail patients would be beneficial. Formulations of synthetic pulmonary surfactants intended for use, require that the in vitro-aerosolisation behaviour with regards to optimal particle size generation and conservation of surface tension, are ideal in order to maintain proper lung function. The objective of this study was to evaluate the suitability of different formulations of a new peptide-containing synthetic pulmonary surfactant Synsurf® during aerosolisation in comparison with the natural surfactants, Curosurf® (porcine) and Liposurf® (bovine). Synsurf®, was synthesised with and without alterations in key components that included cholesterol (1 % and 2 %), palmitic acid (11 %) and tripalmitin (7 %). An extrusion method through polycarbonate membranes with different pore sizes was also included during synthesis of the different formulations. Surfactants were aerosolised with the use of Aeroneb®Pro vibrating mesh nebuliser and particles generated were assessed with a Malvern Zetasizer® and visualised by scanning electron microscopy. Surface tension analyses was determined with a Drop Shape Analyser (DSA25). The main findings of this study showed that nebulisation of non-extruded Synsurf® formulations as well as Curosurf® and Liposurf®, produced a decrease of ± 80 % - 90 % in particle size, that is below the desired distribution range of 1 - 3 d.μm for inhaled particles. However, extrusion included in the synthesis of Synsurf®, generated larger particles post-nebulisation, within the desired range. Nebulisation also significantly influenced the density and viscosity of most Synsurf® preparations and natural surfactants. Additionally, an increase in cholesterol concentration showed a marked increase in viscosity of Synsurf®. With the exception of the original Synsurf® formulation, nebulisation diminished the surface tension lowering ability of all other surfactant preparations. Addition of palmitic acid/tripalmitin and 1 % cholesterol to the original Synsurf® formulation showed an overall pronounced reduction in surface tension in comparison to other formulations. In conclusion, the data of this study indicate that the original formulation of Synsurf® with addition of palmitic acid/tripalmitin and low concentrations of cholesterol, aid in the conservation of the surface tension properties and ideal particle size generation of the surfactant during nebulisation with a vibrating mesh nebuliser.
- ItemA cross-sectional study to investigate the knowledge, attitudes, and current practices of pharmacovigilance, among medical doctors and pharmacists in South Africa(Stellenbosch : Stellenbosch University, 2021-12) Rikhotso, Nyeleti Portia; Page, Carine; Reuter, Helmuth; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medicine: Clinical Pharmacology.Background: Pharmacovigilance pertains to activities aimed at monitoring medicines for related safety concerns, thereby ensuring patient safety and wellbeing. The primary method of pharmacovigilance is spontaneous reporting of adverse drug reactions (ADRs). ADRs have a socio-economic impact when they are not reported and mitigated appropriately. This impact is even more apparent in low-to-middle income countries (LMICs), an economic category encompassing all African countries. The World Health Organisation (WHO) has developed a global pharmacovigilance database (Vigibase®) for countries which are members of the Programme for International Drug Monitoring (PIDM), which includes many African countries. ADR reporting levels however remains low across Africa. This is also true for South Africa, despite being the first African country to become a member of the PIDM in 1992. Therefore, this research study was conducted to investigate the knowledge, attitudes, and practices of pharmacovigilance among medical doctors and pharmacists in South Africa. The aim of this study is to investigate the factors influencing the low adverse drug reporting levels by healthcare professionals in South Africa. Methodology: A cross-sectional survey was conducted in the form of a knowledge, attitudes, and practices (KAP) study design. The targeted sample population was 384 study participants. The questionnaire consisted of closed-ended questions, designed to assess the demographics, knowledge, attitudes, practices of healthcare professionals nationally. The survey also served to obtain suggestions from healthcare professionals to improve ADR reporting in SA. An online survey was created in the survey platform, SurveyMonkey® and the e-link to the survey was shared with the South African Medical Association (SAMA) and the South African Clinical Research Association (SACRA), two professional associations hosting memberships of registered medical doctors and pharmacists in South Africa. Both associations distributed the e-link to their members via email. The obtained data was analysed using IBM SPSS® Statistics version 27. Results: A total of 325 responses were received, accounting for 85% of the target sample population. Most (252; 77.5%) of the study participants on this study received an average score for their knowledge on pharmacovigilance, despite extremely low reported levels (91;28%) of training. Most of the respondents (269; 82.8%,) thought that awareness regarding pharmacovigilance in their professional environment is inadequate. Although the majority (310; 95.4%) of respondents agreed that ADR reporting is their professional obligation, (119; 36.6%) had never seen a reporting form and only (172; 52.9%) had ever participated in ADR reporting. The major factors discouraging respondents from participating in ADR reporting were lack of knowledge on the reporting process and lack of access to the ADR reporting form. The topmost suggestions selected by the respondents to improve ADR reporting in South Africa were to include pharmacovigilance training in the undergraduate curricula of South African universities (266; 81.8%) as well as implementation of on-line or telephonic reporting platforms (235; 72.3%). Conclusion: This study indicates that there is an average level of knowledge of pharmacovigilance amongst medical doctors and pharmacists in South Africa and that they mostly have a positive attitude towards pharmacovigilance. However, this does not translate into acceptable levels of participation in ADR reporting, most likely due to inadequate pharmacovigilance training provided to medical doctors and pharmacists in South Africa.
- ItemA descriptive study to determine the prevalence of TPMT polymorphism in Healthy male subjects in Central South Africa(Stellenbosch : Stellenbosch University, 2014-03) Ferreira, Maria Magdalena; Rosenkranz, B.; Stellenbosch University. Facutly of Medicine and Health Sciences. Department of Medicine. Division of Clinical Pharmacology.ENGLISH SUMMARY : Thiopurine medications e.g. Azathioprine and 6-Mercaptopurine are metabolized by the thiopurine methyltransferase (TPMT) enzyme. This enzyme activity is highly variable due to polymorphism of the TPMT gene. TPMT genotyping can be performed to tailor the treatment with thiopurine medications specifically to the patient's TPMT activity.
- ItemDevelopment of a LC-MS/MS method for the detection of snake venom toxins in human plasma(Stellenbosch : Stellenbosch University, 2022-12) Lermer, Anne; Kellermann, Tracy; Faculty of Medicine and Health Sciences. Dept. of Medicine. Division of Clinical Pharmacology.ENGLISH ABSTRACT: Background: Snakebite envenomation in sub-Saharan Africa significantly threatens human health. Species that was responsible for the envenomation are rarely positively identified. There are no rapid methods/diagnostics available for conclusive identification of the organism/species responsible. Venomous species can be categorised based on the composition and primary effect caused by their venom components as neurotoxic, cytotoxic and/or hemotoxic. Aim: To develop an LC-MS/MS method for the species-specific detection of snake venom toxins from human plasma. Methods: An epidemiological study on the incidence of snakebite in South Africa as reported to Poisons Information Helpline of Western Cape (PIHWC) was performed to provide rationale for the analytical study. Analytical methodology includes identification of species-specific venom toxins by high resolution (HR) LC-MS/MS, fractionation of Naja nivea venom by size exclusion chromatography and compositional analysis of the fractions by HR-LC-MS/MS. Venom fractions were screened for toxicity using a zebrafish model, utilising DanioVision for phenotypic screening and behavioural tracking of the larvae. Thereafter, a triple quadrupole LC-MS/MS method was developed containing species-specific toxins. Results: Analysis of PIHWC call data revealed that in 43.73% of the recorded snakebite cases the causative snake species were unidentified. The snake species Naja nivea, Bitis arietans and Bitis atropos species were identified as most medically significant in South Africa and consequently included in the study. Venom from N. nivea was chosen as the species for fractionation after common peptides from inter-region venom were identified as unique to the species. Behavioural changes in larvae were observed after exposure to sub-lethal concentrations of N. nivea venom fractions. Significant (p<0.0001) changes in larval behaviour were observed in two treatment groups compared to the control. Using transitions that was generated during HR-LC-MS/MS analysis, FASTA files were generated and converted into MRM’s onto the triple quadrupole LC-MS. Toxins were positively identified from human plasma by LC-MS/MS. Discussion: This study identified the species predominantly responsible for snakebites from PIHWC call data, and highlighted a need for a diagnostic to identify the species responsible for envenomation. Analysis of the venom proteomes by HR-LC-MS/MS revealed similarities and differences in the venom profiles of Naja nivea, Bitis arietans and Bitis atropos species. In-solution, HILIC assisted tryptic digestion produced the identification of more proteins from the N. nivea crude venom compared to in-gel digestion and while fractionation by size exclusion chromatography prior to MS analysis increased the detection of low molecular weight toxins. It was also shown that using a combination of conventional HR-MS (with database/library searches) and triple quadrupole MS, a method could be created that identified species specific venom peptides from human plasma to aid diagnosis. Conclusion: This is a proof of concept for future work that will include the development of a lateral flow assay to detect venom from envenomed plasma that is cost-effective to produce, aids in defining diagnosis and importantly serves victims of snakebite envenomation in rural communities.
- ItemDevelopment of LC-MS/MS toxicology screening methods for common poisoning agents in South Africa(Stellenbosch : Stellenbosch University, 2020-12) Tiya, Luthando Lukhanyo; Stander, Marietjie; Kellermann, Tracy; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medicine: Clinical Pharmacology.ENGLISH ABSTRACT: Background: Hospitals admit many patients suffering from acute poisoning on a regular basis. Over a single year period the Tygerberg Poison Information Centre (TPIC) dealt with 4 771 consultations related to human exposure to various poisonous substances. Of these consultations, exposures to medicines and pesticides accounted for the majority of cases. As a response to this medical burden, this project aims to develop effective screening tools for both medicines and pesticides in human plasma. It is believed that such a tool could enhance how medical practitioners accurately treat and respond to serious poisonings. There are many toxicological screening methods employed today. In the past immunoassays (IAs) and gas chromatography coupled to mass spectrometry (GC-MS) were seen to be the gold standard for the identification of compounds. Due to false positive results associated with immunoassays and the labour intensive sample preparation associated with GC-MS, it is clear that there is a need for faster, more robust and more sensitive bioanalytical methods. This study’s objective therefore is to develop a cost effective, fast and robust liquid chromatography tandem mass spectrometry (LC-MS/MS) screening tools for the identification of drugs and pesticides. Relevant drug and pesticide selection was done by consulting with the TPIC, a centre which deals with poisoning cases on a daily basis, as well as clinicians in the Division of Clinical Pharmacology who deal with patients admitted at Tygerberg Hospital daily and CropLife SA, an organisation that has the knowledge of which pesticides are currently in use in South Africa. A total of 37 drugs and 10 pesticides were identified as those often suspected to be involved in poisoning/overdose cases. Two methods were developed: An untargeted liquid chromatography quadrupole time-of-flight mass spectrometry (LC-TOFMS) method for the determination of therapeutic drugs; and a targeted LC-MS/MS method for the determination of pesticides. Method: Analytes were extracted from CPD plasma using protein precipitation (PP). For the untargeted method, a Waters Synapt G2 Quadrupole Time-of-flight (QTOF) mass spectrometer (MS) fitted with an ultra-high performance liquid chromatography (UHPLC) was used. The separation was done using a Waters HSS T3 (1.8 μm, 2.1 ×150 mm) column. A gradient consisting of a mobile phase of 0.1% formic acid in both water (A) and in acetonitrile (B) at a flow rate of 0.25 mL/min. Ionisation mode was set for both positive and negative (ESI +/-); Nitrogen as the desolvation gas was set at a flow rate of 650L/h; Desolvation temperature was set at 275˚C. The instrument was operated in the MSE mode. The total run time was 37 min. Four concentration levels (10, 50, 100, 1000 ng/mL) were determined to cover the pharmacokinetic peak concentrations of all drugs. This range was determined according to sub-therapeutic, therapeutic and overdose type concentrations. Furthermore, the data generated from the untargeted method development process was used to accurately identify analytes using online search libraries. For the targeted method, two liquid chromatographic separation methods were developed on a Shimadzu 8040 LC-MS/MS instrument. One gradient method using the Agilent Poroshell 120 EC-C18 (2.7 μm, 4.6 ×100 mm) column was developed for atrazine, MCPA, fipronil, methomyl and aldicarb, while a second isocratic method utilizing of the Restek Raptor Biphenyl (2.7 μm, 2.1 x 100 mm) column was also developed for imidacloprid. Both methods used mobile phase consisting of 0.1% formic acid in water (A) and in acetonitrile (B) with a flow rate of 0.5 mL/min. The LC program on the Poroshell method starts at 30% (B) for 2 min followed by a 0.5 minute ramp to 90% (B); 2.5 min at 90% (B); 0.5 min to 30% (B), equilibrate at 30% (B) for 2.5 min. The total run time is 9 min. The biphenyl method isocratic run comprises of (65%:35%, v/v) for a run time of 1.75 min. A semi-quantitative method with a quadratic curve fit with 1/x regression over the range of 20 to 600 ng/mL was chosen. The two targeted methods were subjected to a partial validation to ensure that the methods were accurate, robust and reliable. Results: The untargeted method was able to detect and identify 92% of the therapeutic drugs included in the screen. Due to matrix effects and differences in compound ionisation some could not be detected at lower concentrations. Polarity and thus lack of retention on the columns, difficulty in ionisation, and the inability to produce stable fragments made the detection of valproate, levetiracetam and metformin not possible on the method. A screening tool for simultaneous determination of pesticides was optimized. Due to several challenges associated with the LC-MS/MS determination of glyphosate, paraquat and deltamethrin, the study resorted to excluding these three pesticides from the current methods. The targeted method was developed for the determination of seven pesticides. The USA Food and Drug Administration (FDA) and the European Medicines Agency (EMA) guidelines were followed for a partial validation of the semi-quantitative method. Three independent runs were assessed to measure accuracy and precision. The calibration curve was linear over the ranges 20 to 600 ng/mL. Matrix effects, recovery, process efficiency, on-bench stability, freeze/thaw stability, storage stability, and whole blood stability for the methods was successfully determined for the seven pesticides. Conclusion: To respond to the medical burden of acute poisoning cases faced by our hospitals, this study has developed efficient screening tools for both relevant medicines and relevant pesticides in human plasma. The latter method was subjected to a partial validation, ensuring accuracy and reliability of results that will be applied to the clinical management of poisoning patients.
- ItemDrug-drug interactions between antiretrovirals and fluconazole in HIV-infected patients(Stellenbosch : Stellenbosch University, 2012-03) Fouche, Desire; Rosenkranz, Bernd; Stellenbosch University. Faculty of Health Sciences. Dept. of Medicine. Pharmacology.ENGLISH ABSTRACT: Background: HIV-positive patients have a significantly weakened immune system which makes them highly susceptible for opportunistic infections, requiring additional treatment. Cryptococcal meningitis and oropharyngeal candidiasis are treated with oral fluconazole. A great potential for drug-drug interactions (DDIs) between fluconazole and antiretrovirals (ARVs), efavirenz, nevirapine, and lopinavir/ritonavir, exists due to interference in common metabolic pathways. The outcome may result in the development of adverse drug reactions or drug resistance and treatment failure. Aim: The primary aim of this thesis was to evaluate the effect of fluconazole on the pharmacokinetics of efavirenz, nevirapine and lopinavir/ritonavir in HIV-infected patients diagnosed with cryptococcal meningitis or oropharyngeal candidiasis. Methods: A prospective study was conducted in 80 HIV-positive, treatment experienced adults (≥18 years old) treated in three different outpatient clinics in the Western Cape region. Patients were subdivided according to ARV regimen and the use of fluconazole. A sparse sampling design was used and corresponding ARV serum concentrations were determined by established HPLC and GC methods. Fluconazole serum concentrations were determined by a newly developed HPLC method. Patient characteristics, concomitant medications, clinical test data and ARV serum concentrations were included in a NONMEM generated, onecompartment, open pharmacometric model with first order elimination to detect any drugdrug interactions between fluconazole and the studied ARVs. The secondary outcome was to establish which patient characteristics influence ARV pharmacokinetics. Results: From 80 outpatients, a total of 276 ARV serum samples (137 efavirenz, 67 nevirapine and 72 lopinavir) were collected for pharmacokinetic evaluation. Efavirenz clearance was correlated with race and concomitant use of rifampicin. No significant covariates were established in the nevirapine model. In the lopinavir model, concomitant use of clotrimazole and the antituberculosis combination isoniazid, pyrazinamide and rifampicin were identified as significant covariates. Discussion: No significant effects of fluconazole on the pharmacokinetics of any of the studied ARVs were observed. Varying efavirenz plasma concentrations in different ethnic populations may be due to differences in gene expression particularly CYP2B6. Coloured patients had significantly lower efavirenz serum concentrations (56.8% decrease in clearance), which has not been previously described in the South African context. Although gender was not a significant covariate in the nevirapine model, female patients tended to have higher nevirapine serum concentrations. TB treatment in all patients receiving lopinavir consisted of a combination of isoniazid, pyrazinamide and rifampicin, each with different effects on CYP isoenzymes. The exact contributing factor of each drug in the ultimate decrease in lopinavir clearance (46.4%) can therefore not be established. Conclusions: Given the limitations of the sample size in the present study, no statistical significant effect of fluconazole on the pharmacokinetics of the investigated ARVs could be demonstrated. A retrospective analysis of the data showed various co-factors that influence the pharmacokinetics of the investigated ARVs. This data needs to be confirmed in a prospective study as the identified covariates are appropriate in the management of HIVinfected patients in the South African context.
- ItemThe effect of dolutegravir on adipose tissue health(Stellenbosch : Stellenbosch University, 2022-10) Coetzee, Johanna Adriana; Smith, Carine; Ross, Kelly Shirley; Faculty of Medicine and Health Sciences. Dept. of Medicine. Division of Clinical Pharmacology.ENGLISH ABSTRACT: Introduction: Dolutegravir, an integrase strand transfer inhibitor (INSTI), forms part of the first-line antiretroviral (ARV) therapy. Despite low cost, fewer drug-drug interactions and minimal reported side effects, dolutegravir use has clinically been associated with weight gain. The significance of this in terms of adipose- and overall patient health remains to be fully elucidated. Methods: The effects of dolutegravir on the adipose tissue health were assessed in a 12-week treatment intervention study in Wistar rats, allowing an assessment of risk profile for dolutegravir in the absence of potential confounding effects of retroviral infection or other ARV agents commonly found in combination therapy. Dolutegravir was administered as a human equivalent dose set in jelly blocks, once daily for 12 weeks, starting at 8 weeks of age. Visceral adipose tissue morphology and fibrosis profile, adipokine and inflammatory cytokine levels were assessed. Results: Dolutegravir did not change the rate of body mass increase in the rats (when compared to a placebo group). Females presented to have smaller adipocyte size and increased adiponectin secretion – more pronounced in the treated group compared to the controls. While pro-inflammatory cytokines (TNF-α and MCP-1) were also elevated in both the female groups compared to the males. Conclusion: Current data illustrates that in terms of potential effects of dolutegravir on AT health, females seem more vulnerable to undesired longer term outcome. The overall small effect sizes seen is in line with a chronic, low-grade dysregulation which may predispose dolutegravir-treated patients to development of co-morbidities with a chronic inflammatory character.
- ItemThe effect of Dolutegravir on redox and vascular integrity(Stellenbosch : Stellenbosch University, 2022-10) Conradie, Janica; Smith, Carine; Ollewagen, Tracey; Faculty of Medicine and Health Sciences. Dept. of Medicine. Division of Clinical Pharmacology.ENGLISH ABSTRACT: Background: Of the estimated 7.2 million people living with HIV (PLWH) in South Africa, more than 50% are on antiretroviral (ARV) medication. Dolutegravir (DTG), an integrase strand transfer inhibitor (INSTI), is increasingly used in South Africa (and Africa) as one of the first line treatments for HIV. Both in vitro and clinical studies indicate that DTG-based therapies have been associated with adverse effects (such as abnormal weight gain, hyperglycemia, and neurological dysfunction) alongside increased oxidative stress. Another disease state common in the South African context is obesity. DTG is administered to an individual regardless of their weight. As obesity is also associated with oxidative stress and inflammation, this might be a potential confounding factor in the efficacy and safety of DTG treatment. Endothelial dysfunction is one of the most common risk factors associated with non-communicable disease (such as obesity and CVD) and would therefore be an important phenomenon to investigate in the context of ARVs and obesity. Aim: This study aimed to elucidate potential effects of chronic DTG on redox profile and endothelial integrity in the presence or absence of overfeeding as a confounder. Methods: Adult zebrafish were subjected to chronic administration of DTG in the absence and presence of obesity (overfeeding model) over a period of 2 weeks. The lean zebrafish received Hikari dry pellets twice per day, whereas the overfed fish received the same food, six times per day over 4 weeks. A parallel 12-week DTG administration study was also executed in lean male and female Wistar rats. Body mass, reactive oxygen species (ROS) levels (hydrogen peroxide (H2O2)) and vascular endothelial tight junctions (claudin-5 and ZO-1) and adherens junction (VE-Cadherin) protein profile were evaluated. Results: DTG did not have a significant effect on the body mass of adult zebrafish or rats. DTG administration showed no detrimental effect on ROS levels in either zebrafish or rats. When considering the effect of DTG on the expression of tight and adherens junction proteins, DTG showed no effect on the expression of ZO-1 and Claudin-5 in both zebrafish and rats. In terms of obesity, the overfed zebrafish had significantly higher body mass when compared to lean fish confirming successful execution of the overfeeding protocol. Overfeeding did not impact ROS, however there was a decrease in VE-cadherin expression in the zebrafish dorsal aorta, pointing to a cumulative effect of DTG and obesity (overfeeding). Conclusion: This study suggests that in the absence of HIV, DTG does not have an effect on redox status and endothelial dysfunction in terms of tight and adherens junction integrity. However, the addition of overfeeding highlighted the cumulative effect of DTG and obesity on endothelial function, an effect that can potentially impact the human population.
- ItemEffect of ultrasound on transdermal permeation of diclofenac and the temperature effects on human skin(Stellenbosch : University of Stellenbosch, 2005-12) Basson, Erina; Van der Bijl, P.; Van Eyk, A. D.; University of Stellenbosch. Faculty of Health Sciences. Dept. of Medicine. Pharmacology.During the last two decades the effects of ultrasound on the transdermal diffusion of a wide variety of drugs have been extensively investigated. Because there is much uncertainty regarding the efficacy of and mechanisms involved in this mode of permeation enhancement, the objective of the study was to investigate the effect of ultrasound on the transdermal permeation of the nonsteroidal anti-inflammatory drug, diclofenac. For this purpose a dual-stage experimental design and a continuous flow-through diffusion system was used. Therapeutic levels of continuous ultrasound of 3 MHz at an intensity of 2 W/cm2 for 10 min, were used. It was clear from the present study that ultrasound enhanced the permeability of human skin to diclofenac released from a commercially available gel. These results were in contrast with those obtained for ibuprofen in an in vitro study across human skin, but in agreement with those obtained in two in vivo studies of the latter nonsteroidal anti-inflammatory drug. Steady state flux values of diclofenac remained approximately 1.26 times higher than those of controls during the 24 h of the experiment. These observations concurred with those made in two previous in vivo studies. Furthermore, the in vitro flow-through diffusion model was shown to have predictive value as an in vivo method for sonophoresis. Temperature-dependent flux rates for 3H2O across human skin were also studied. The mechanistic effects of ultrasound on the permeability characteristics of human skin have been reported on in a number of studies. Although various mechanisms have been proposed, there is no consensus regarding their relative importance. In addition the temperature-dependent flux changes of 3H2O across human skin were investigated using a continuous flow-through diffusion system. The same ultrasound parameters as in the permeability experiments were used. The results obtained showed that temperature increases of approximately 10 °C occurred following sonication. The flux changes of 3H2O across human skin between 37 °C and 42 °C were shown to be reversible. The results from the present study do not support the sonication-heating theory in which permeability changes in skin are primarily attributed to thermally-induced changes in stratum corneum lipids. It was therefore concluded that the enhancement of diclofenac permeation by sonication could not be adequately explained primarily on a thermal basis.
- ItemEvaluation of the effectiveness of dose individualisation to achieve therapeutic vancomycin concentrations(Stellenbosch : Stellenbosch University, 2017-12-05) Abulfathi, Ahmed Aliyu; Decloedt, Eric; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences. Dept. of Medicine. Division of Clinical Pharmacology.ENGLISH ABSTRACT: Background The glycopeptide antibiotic vancomycin is used for treatment of methicillin resistant Gram positive cocci. Adequate vancomycin plasma concentrations are related to bacterial cure. However, inter- and intra-patient variability make it difficult to achieve therapeutic vancomycin concentrations. The primary objective of this study was to determine the effectiveness of using computerised therapeutic drug monitoring (TDM) to assist in achieving therapeutic vancomycin concentrations at a tertiary hospital in South Africa. Method This was a 2-period study consisting of a retrospective 1-month observational period followed by a prospective 1-month period where computerised TDM was implemented as an intervention to assist with vancomycin dose individualisation. Prescribers were provided with guidelines on vancomycin dosing and TDM results during both study periods. During the prospective period, all vancomycin TDM results were followed by dose individualisation using computerised TDM. In addition, the area under the-concentration-time curve over minimum inhibitory concentration (AUC/MIC) was calculated to ensure a ratio of ≥400. Results The retrospective study included 77 patients with 292 vancomycin concentrations: 69% (53/77) adult and 31% (24/77) paediatric patients. The prospective study included 80 patients with 217 vancomycin concentrations measured: 69% (55/80) adult and 31% (25/80) paediatric patients. Less vancomycin TDM data were requested during the prospective period with a median (interquartile range) of 2 (1-3) samples per patient compared with 3 (1- 5) during the retrospective period. The odds ratio of achieving therapeutic trough concentrations was 3.63 (95% confidence interval (CI): 1.81 - 7.3) in the prospective period when TDM-adjusted vancomycin dosing and correct TDM procedures were applied. The use of computerised TDM in patients on continuous infusion resulted in 26% improvement in achieving therapeutic vancomycin concentrations in the prospective period (odds ratio 2.96; 95% CI: 1.19 - 7.36). In the prospective period, AUC0-24 was 400 mg·h/L or above in 71% of occasions. Conclusion The correct use of computerised TDM results in a higher frequency of therapeutic vancomycin concentrations in a middle income setting. Trough vancomycin concentrations alone correlate poorly with AUC0-24. Achieving therapeutic vancomycin concentration may strengthen antibiotic stewardship and save on TDM resources.
- ItemExploring and identifying the indigenous healers of madwaleni and their relationship with ethnobotany and healthcare(Stellenbosch : Stellenbosch University, 2019-04) May, Thandokazi; Mji, Gubela; Reuter, Helmuth; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medicine: Clinical Pharmacology.Rationale: The use of indigenous medicine is widely known in South Africa. In fact, it is estimated that 80-85% of black South Africans consult with indigenous healers in both rural and urban communities (Moshabela, et al., 2016). Despite increased academic interest in indigenous health knowledge (IHK) in the country, there is still interest in studies that are aimed at documenting the indigenous practitioners as well as their herbs and plants. Suggestions have been made to fill this knowledge gap by conducting ethnobotanical surveys of the plants used by indigenous healers as well as to identify who are these healers that use these plants. Aim and Objectives: The main aim and objective of this study was to explore and identify the indigenous healers of the Madwaleni, including the illnesses these healers manage, and which herbs are used to treat each illness. Other objectives were to: catalogue the ethnobotanical diversity used by these healers, and to identify the precise botanical environment that these herbs grow as well as the relationship these healers have with these environments. Lastly, the study explores the relationship between indigenous healers and the biomedical health care system in the area. Method: This is a descriptive, ethnographic study that used qualitative methods of data collection. The data was collected through participant observation, where participants took part in interviews and Focus Group Discussions (FGDs). There were 37 participants and key stakeholders, 30 being practitioners of indigenous medicine, 5 being biomedical health professionals, and 2 being traditional leaders. Both in-depth interviews and FGDs were used to collect data, totalling up to 6 interviews and 15 FGDs. Life stories were documented as part of exploring methods that could be used in the reconciliation process. The plants used by the indigenous healers of the area were documented transcriptionally and photographically. Findings: • The indigenous healers of Madwaleni can be categorized in five categories: (1) amaGqirha (indigenous doctors) and (2) amaXhwele (herbalists), (3) elite older Xhosa women and (4) amaTola (older elite men), and (5) abaThandazeli (faith healers). Intersectionality and partnerships between these groups of healers was welcomed and encouraged, although some unresolved tensions exist between the healers due differences in philosophy and practice. • The relationships between the individual, the community, the natural environment and the ancestral spirits all play a pivotal role in maintaining health in Madwaleni. Therefore, health is attained when the complete balance between mind, body and soul is achieved through the maintenance of solid relationships between all members of society, including the ancestors and the natural environment. When sickness results because of rifts in these relationships, indigenous medicinal plants must be administered to treat the illness and to regain the normal state of health. These plants are believed to be imbued with the spiritually healing powers of the natural environments in which they grow. Consequently, indigenous amaBomvana medicines have not only a healing function, but also have an apotropaic spiritually protective function. • Tensions continue to dominate the landscape between indigenous health knowledge and Western knowledge in Madwaleni. Biomedical professionals in the area cite the lack of empirical evidence for the pharmacological functions of indigenous medicines as the reason behind their refusal to accept IHK as a valid health system. Conclusion: Considering the cultural understanding of well-being and the determinants of health, the amaBomvana prefer to utilize diverse health management strategies when it comes to managing and treating illness. The health strategies of the amaBomvana people are exceptional and have the potential to help unlock some of the medical challenges of the modern world. The existence and endurance of various indigenous healers and their IHK strategies in the face of the threat of biomedicine is attestation to this. There exists a lot of unresolved tension between the various groups of healers in the area, due to differences in ethnomedical practice and philosophy. Before a partnership can be formed with the biomedical field, the indigenous healers themselves would need to share and acknowledge each other without taking any position of superiority over each other. The unresolved relationship between biomedicine and the indigenous health system creates spaces of confusion for the patients of Madwaleni, often resulting in bad health decision making and mismanagement of disease. A reconciliation process model is recommended by the study in order to repair this.
- ItemInhibitory effect of selected herbal supplements on CYP450-mediated metabolism : an in vitro approach(Stellenbosch : Stellenbosch University, 2016-03) White, Charlize; Rosenkranz, Bernd; Bouic, Patrick J. D.; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medicine. Clinical Pharmacology.ENGLISH ABSTRACT: INTRODUCTION Herbal products are popularly used as complementary and alternative medicines to treat a variety of conditions. Often patients use them in conjunction with conventional medicines. Herbal products contain many pharmacologically active phytochemicals that may interfere with the absorption, distribution, metabolism, and elimination of medicines. This interaction can lead to an increase of the plasma concentrations of other medicines to toxic levels, or to their decrease below therapeutic levels, resulting in lack of efficacy. The liver cytochrome P450 (CYP) enzymes are responsible for the metabolism of a large majority of medicines. In order to provide more information on the potential interaction between African herbal medicines and conventional medicines, the present study has investigated the inhibition of selected CYP enzymes by three popular South African medicinal plants, Buchu, African ginger, and Warburgia salutaris. METHODS Buchu capsules, African ginger, and Warburgia salutaris tablets were obtained in a local pharmacy. 60% methanol/water extracts were prepared and analysed by GC-MS to reveal the composition of the volatile components of each product. Fluorogenic inhibition assays were conducted using Vivid® recombinant CYP screening kits according to the manufacturer’s protocol. This protocol included the pre-incubation of herbal extracts, recombinant CYP isoform and cofactor solution. The metabolic reaction was initiated by the addition of CYP-specific substrate and NADP+; the solution was incubated for 30 minutes at 37°C, after which fluorescence was measured using a microplate reader. The percentage remaining activity was calculated and used to determine the IC50 values of each herbal product. Time - dependent inhibition (TDI) was evaluated using the normalized ratio, NADP+-, concentration -, and time - dependent approaches. RESULTS The GC-MS analysis revealed monoterpenes, sesquiterpenes, and alkane hydrocarbons in the volatile component. Warburgia salutaris, African ginger, and Buchu inhibited CYP2C19 with IC50 values of 5.88 μg/ml, 32.38 μg/ml, and 53.52 μg/ml, respectively. Likewise, the IC50 values of 5.64 μg/ml, 1.09 μg/ml, and > 100 μg/ml were obtained for inhibition of CYP3A4 by Warburgia salutaris, African ginger, and Buchu, respectively. Using the normalized ratio, Warburgia salutaris and African ginger showed time- and concentration - dependent inhibition of CYP1A2, and Buchu showed intermediate TDI effects that were not concentration dependent. All three extracts showed TDI of CYP3A4; the inhibition displayed by Buchu and Warburgia salutaris was NADP+ dependent. African ginger was the only extract to show NADP+ dependent inhibition of CYP1A2. A kinetic TDI assay Stellenbosch University https://scholar.sun.ac.za iii showed that the IC50 value of African ginger decreased over time, indicating TDI. Warburgia salutaris was not a time-dependent inhibitor of CYP3A4, and Buchu may have a limited time-dependent inhibitory effect. CONCLUSION Warburgia salutaris, African ginger, and Buchu have the potential to cause clinically relevant herb-drug interaction, if sufficient concentrations are achieved in vivo. Further studies are needed to confirm this finding.
- ItemKarakterisering van die katalase van BCG : invloed van isoniasied op die gesuiwerde ensiem(Stellenbosch : Stellenbosch University, 1990-12) Basson, Karen; Van Zyl, J. M.; Van der Walt, B. J.; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Clinical Pharmacology.ENGLISH ABSTRACT: Catalase was extracted and isolated from BCG bacilli by the following precedures : sonication, treatment with deoxyribonuclease, treatment with octyl glucoside and sonification, ammonium sulphate precipitation, hydroxyapatite chromatography and chromatography on Sephacryl S-1000. A significant increase in the specific activity of the catalase and peroxidase functions was observed during purification and a final purity index (A405/A280) of 0.258 was obtained. Only one protein band, in addition to aggregates which could hardly penetrate the gel, was observed after non-denaturing polyacrylamide gel electrophoresis of the purified enzyme. The peroxidase activity (ABTS) assay) was consistent with the protein band. A.M. of 163.1 kDa was calculated from results obtained with SDS polyacrylamide gel electrophoresis, which correlates with a Mr of 144.54 kDa obtained by gelfiltration studies on Sephacryl S-1000. A characteristic Soret peak at 405 nm was observed on the UV spectrum of the purified enzyme. The optimum pH for catalase activity was 8,0. At pH 7,0 81% of the maximum activity at pH 6,0 and 56% at pH 9,0. This correlates with the fact that catalase must be able to survive over a broad pH range.
- ItemLC-MS/MS methods for the quantification of sulfasalazine and sulfapyridine in various matrices: application to a pharmacokinetic study(Stellenbosch : Stellenbosch University, 2022-11) Louw, Vanessa; Kellermann, Tracy; Faculty of Medicine and Health Sciences. Dept. of Medicine. Division of Clinical Pharmacology.ENGLISH ABSTRACT: Introduction: An early phase clinical trial which took place at The Mercy Hospital for Women in Australia assessed the use of sulfasalazine as a treatment for preterm pre-eclampsia. This project consisted of the development and validation of a Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) method according to the Food and Drug Administration (FDA) and European Medicines Agency (EMA) guidelines to simultaneously quantitate sulfasalazine and its metabolite, sulfapyridine, in placenta for pharmacokinetic analysis. Methods: A Shimadzu 8040 mass spectrometer was operated in multiple reaction monitoring (MRM) mode to monitor the mass-to-charge (m/z) transition of the protonated precursor ions m/z 398.90 and m/z 250.07 to the product ions m/z 381.05 and m/z 156.00 for sulfasalazine and sulfapyridine, respectively. Sulfasalazine-d4 and sulfapyridine-d4 were used as internal standards. 100 μL of placental tissue homogenate was extracted using acetonitrile:methanol (90:10, v/v) and the supernatant was eluted through hydrophilic-lipophilic balanced cartridges. The extraction procedure was followed by liquid chromatographic separation using a Poroshell C18 column. Gradient elution using a mobile phase combination of water + 0.1% formic acid (A) and acetonitrile:methanol (90:10, v/v) + 0.1% formic acid (B) was used. Accuracy and precision were assessed over three consecutive, independent runs. The ratios of analyte peak area to internal standard peak area were plotted against the nominal concentrations to generate a calibration curve which fits a quadratic regression (weighted by 1/x, x= concentration) over the range 30-30 000 ng/mL for both sulfasalazine and sulfapyridine. Results and Discussion: The average accuracy of calibration standards during inter-day validations ranged from 94.2-103.2% (%CV= 1.4-10.8) for sulfasalazine and 96.6-103.4% (%CV= 1.4-8.3) for sulfapyridine. The accuracy of quality controls ranged from 101.6-112.7% (%CV= 4.4-6.7) and 97.4-108.4% (%CV= 3.7-10.0) for sulfasalazine and sulfapyridine, respectively. Endogenous matrix components were shown to have no impact on the reproducibility of the method when placental tissue from six different sources were analysed. The average recovery of sulfasalazine and sulfapyridine from placental tissue homogenate was 121.5% and 119.6%, respectively. Autosampler stability experiments indicated that placental tissue homogenate extracts were stable on instrument for up to 48-hours at the method-defined temperature. Re-injection reproducibility experiments illustrated that the method remained accurate and precise for analysis of both analytes following a re-injection of a batch for up to 48 hours after the initial injection. Furthermore, sulfasalazine and sulfapyridine were found to be stable in placental tissue homogenate for 10 days when stored at -80 °C, for six hours when left on bench at room temperature, and when subjected to three-freeze thaw cycles. Upon analysis of patient samples (n= 9), the concentrations ranged from 491-4201 ng/g tissue for sulfasalazine and 637-26756 ng/g tissue for sulfapyridine, with two patient samples below the limit of quantitation (BLQ) of the assay for both analytes. Conclusion: An LC-MS/MS method for the quantification of sulfasalazine and sulfapyridine in human placenta was successfully validated and applied to a clinical study to evaluate the efficacy of sulfasalazine as an intervention for pre-eclampsia.
- ItemNeurological risk of prolonged low dose exposure to imidacloprid in zebrafish(Stellenbosch : Stellenbosch University, 2022-11) McCulloch, Megan; Kellermann, Tracy; Smith, Carine; Faculty of Medicine and Health Sciences. Dept. of Medicine. Division of Clinical Pharmacology.ENGLISH ABSTRACT: Imidacloprid (IMI) is a systemic neonicotinoid insecticide intended to replace the organophosphate pesticides in agriculture. Extensive use of these pesticides increases the risk to the environment and non-target organisms such as humans due to their potential bioaccumulation and toxicity. Researchers studying the effect of IMI on human nicotinic receptors (α4β2) have reported that IMI may have more substantial side effects on humans than originally anticipated. This research project aimed to assess the possibility of long-term neurological risks following prolonged, low dose IMI exposure within an in vivo zebrafish model. Methods A protein precipitation extraction from zebrafish brain, liver and gill homogenate was applied followed by LC-MS/MS detection of neurotransmitters and IMI and its primary metabolites. Protein precipitation was conducted using methanol:acetonitrile (1:1 v/v) as the precipitating solvent. Phenethylamine-d4 and IMI-d4 were used as internal standards for the neurotransmitter and IMI LC-MS/MS methods, respectively. For the neurotransmitters, chromatographic separation was achieved using a Poroshell column (3.0 x 100 mm, 2.7 μm) using a gradient elution mode at a flow rate of 0.45 mL/min and an analysis time of 7 min. Mobile phase A and B consisted of water with 0.1% formic acid and acetonitrile, respectively. For IMI and its metabolites, chromatographic separation was achieved using a biphenyl column (2.1 x 100 mm, 2.7 μm) with gradient elution at a flow rate of 0.4 mL/min. The total analysis time was 8.5 min. Mobile phase A and B consisted of water and methanol respectively, both with 5 mM ammonium formate and 0.1% formic acid. The two developed methods underwent a partial validation to certify that both methods were precise, accurate and reliable. Zebrafish larvae were exposed to IMI at four and five days post fertilisation to determine the no observed adverse effect level (NOAEL) of IMI. After this, adult zebrafish were exposed to the NOAEL concentration for 21 days. Key endpoints included behaviour indicative of neurocognitive decline and possible bioaccumulation in the adult zebrafish brain, liver and gills. Neurotransmitter concentrations were measured in the adult zebrafish brain tissue at the end of the treatment period to evaluate changes in neurotransmitter signalling and potential neurological risks using the developed LC-MS/MS method. Bioaccumulation of IMI and its metabolites in zebrafish brain, liver and gills was evaluated using LC-MS/MS. Results The calibration curve fits a quadratic (weighted 1/C) regression over the concentration range of 31.3 - 1000 ng/mL for acetylcholine, gamma-aminobutyric acid, serotonin and dopamine. The calibration curve for IMI and its metabolites fits a quadratic (weighted 1/C) regression over the concentration range of 1.95 - 125 ng/Ml for imidacloprid-urea and IMI, 0.244 - 125 ng/mL for desnitro-imidacloprid and 3.91 - 125 ng/mL for 5-hydro imidacloprid. The NOAEL of IMI in zebrafish larvae was determined to be 2.5 μg/L. No significant morphological changes were observed in the adult zebrafish during the treatment period. Behavioural changes observed during the pesticide exposure period included decrease in appetite of the treatment group. The treatment group was also observed swimming at the bottom of the tank in comparison to the control group. Although IMI, IMI-urea and desnitro-IMI could not be detected in any of the tissue specimens, 5-hydro IMI was detected at relatively high concentrations in the liver (0.793 ng/mg tissue) and gill epithelial tissue (117 ng/mg tissue). Only concentrations of gamma-aminobutyric acid and acetylcholine were detected and quantified in both the treated and control group. The treated group showed a 1.4-fold decrease and 1.9-fold increase in acetylcholine and gamma-aminobutyric acid, respectively in comparison to the control. Serotonin and dopamine could not be detected due to their levels being below the limit of quantitation of this method. Conclusion Robust LC-MS/MS methods were developed for the detection and quantitation of IMI, desnitro-imidacloprid, imidacloprid-urea and 5-hydro-imidacloprid, as well as serotonin, dopamine, acetylcholine and gamma-aminobutyric acid neurotransmitters in 200 μL zebrafish brain, liver and gill epithelial tissue homogenate. The behavioural changes observed in the adult zebrafish could be an indication of one of two things, anxiety or sedative effect. This is verified by the increase in gamma-aminobutyric acid neurotransmitter levels. Together with the evaluation of bioaccumulation of imidacloprid and its metabolites within the brain, liver and gill epithelial tissue of zebrafish, this study provides an indication of the potential risk to human health following chronic neonicotinoid exposure. Overall, our findings further contribute to existing literature and suggest that IMI does pose a threat to more than just insects and therefore requires further investigation.