Browsing by Author "Rosenkranz, Bernd"
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- ItemAssociation between health-related quality of life and medication adherence in pulmonary tuberculosis in South Africa(Frontiers Media, 2017-12-18) Kastien-Hilka, Tanja; Rosenkranz, Bernd; Schwenkglenks, Matthias; Bennett, Bryan M.; Sinanovic, EdinaBackground: Health-related quality of life (HRQOL) and adherence to treatment are two often inter-related concepts that have implications for patient management and care. Tuberculosis (TB) and its treatment present a major public health concern in South Africa. The study aimed to evaluate the association between HRQOL and adherence in TB patients in South Africa. Methods: Four self-reported HRQOL and one self-reported adherence measures were used in an observational longitudinal multicentre study during 6-month standard TB treatment. These included the generic Short-Form 12 items (SF-12) and European Quality of Life 5 dimensions 5 levels (EQ-5D-5L), the disease-specific St. George's Respiratory Questionnaire (SGRQ) and the condition-specific Hospital Anxiety and Depression Scale (HADS) for HRQOL. Adherence was measured by the Morisky Medication Adherence Scale 8 items (MMAS-8). The relationship between both concepts was examined in 131 patients using Spearman's rho correlations, and linear regression models. Results: HRQOL improved over 6-month TB treatment, whereas adherence mean scores stayed constant with participants attaining a medium average level. Around 76% of patients reported to be high adherers and 24% were reporting a medium or low adherence. Associations between HRQOL and adherence were mainly weak. High adherence at treatment start was positively related to improvements in anxiety and depression after 6-month treatment. The overall improvement in pain and discomfort, and psychosocial health aspects over treatment time was positively, but weakly associated with adherence at 6 months of treatment. Conclusion: A positive relationship exists between adherence and HRQOL in TB in a South African setting, but this relationship was very weak, most likely because HRQOL is affected by a number of different factors and not limited to effects of adherence. Therefore, management of TB patients should, besides adequate drug treatment, address the specific mental and psychosocial needs.
- ItemB-cell and T-cell activation in South African HIV-1-positive non-Hodgkin’s lymphoma patients(Medpharm Publications, 2018) Flepisi, Brian T.; Bouic, Patrick; Sissolak, Gerhard; Rosenkranz, BerndBackground: Altered immune mechanisms play a critical role in the pathogenesis of non-Hodgkin’s lymphoma (NHL). HIV-1 (HIV) infection is associated with a state of excessive T-cell activation, which can lead to increased T-cell turnover and lymph node fibrosis. Objectives: This study aimed to determine the serum levels of circulating B-cell activation markers, and the expression of T-cell activation and regulatory markers in HIV-positive NHL patients. Method: The serum levels of circulating soluble(s) sCD20, sCD23, sCD27, sCD30 and sCD44 molecules, all of which are biomarkers of B-cell activation, were determined by enzyme-linked immunosorbent assays (ELISA), while biomarkers of T-cell activation (CD8+CD38+) and regulation (FoxP3) were determined by flow cytometry in 141 subjects who were divided into five groups: Combination antiretroviral therapy (ART)-naïve HIV-positive patients; ART-treated HIV-positive patients; HIV-negative NHL patients; HIV-positive NHL patients on ART; and healthy controls. Results: HIV-positive NHL patients had significantly higher serum levels of sCD20, sCD23, sCD30 and sCD44 than HIV-negative NHL patients, while all five biomarkers were significantly elevated in HIV-positive NHL patients when compared with ART-treated HIV-positive patients. HIV-positive NHL patients had higher CD8+CD38+ and lower FoxP3 expression than HIV-negative NHL and ART-treated HIV-positive patients. Conclusion: B-cell activation is increased in HIV-positive NHL patients and is associated with reduced regulatory T-cell populations and increased CD8+ T-cell activation.
- ItemBiomarkers of HIV-associated cancer(Libertas Academica, 2014) Flepisi, Brian Thabile; Bouic, Patrick; Sissolak, Gerhard; Rosenkranz, BerndCancer biomarkers have provided great opportunities for improving the management of cancer patients by enhancing the efficiency of early detection, diagnosis, and efficacy of treatment. Every cell type has a unique molecular signature, referred to as biomarkers, which are identifiable characteristics such as levels or activities of a myriad of genes, proteins, or other molecular features. Biomarkers can facilitate the molecular definition of cancer, provide information about the course of cancer, and predict response to chemotherapy. They offer the hope of early detection as well as tracking disease progression and recurrence. Current progress in the characterization of molecular genetics of HIV-associated cancers may form the basis for improved patient stratification and future targeted or individualized therapies. Biomarker use for cancer staging and personalization of therapy at the time of diagnosis could improve patient care. This review focuses on the relevance of biomarkers in the most common HIV-associated malignancies, namely, Kaposi sarcoma, non-Hodgkin’s lymphoma, and invasive cervical cancer.
- ItemComparative study of different brands of stavudine capsules for the off-label 'opened capsule' dosing method recommended for HIV-infected infants and children in resource-limited settings(Health and Medical Publishing Group, 2009) Innes, Steve; Smuts, Marlize; Cotton, Mark F.; Seifart, Heiner; Rosenkranz, BerndIntroduction. If a caregiver does not have access to a refrigerator, the South African National Department of Health advises that stavudine adult capsule formulations be employed using the off-label 'opened capsule' dosing method. The accuracy of this dosing method has not previously been validated. Aim. To assess the accuracy of the off-label opened capsule method for stavudine dosing in infants and children. In addition, we assessed the relative ease of dispersion of generic and original capsule preparations in water to determine which preparations, if any, are suitable for the off-label opened capsule dosing method. Method. We evaluated 10 Zerit (Bristol-Myers Squibb), 5 Stavudine (Aspen), and 5 Stavir (Cipla) capsules. Each capsule was dispersed in 30 ml water, creating 20 separate solutions. Timed dispersion of each generic was compared with that of the original (Zerit). Each solution was then centrifuged to remove sediment, and the concentration of active drug (mg/ml) was analysed by high-performance liquid chromatography. Results. The ease of dispersion of the contents of Aspen Stavudine capsules was equivalent to that of Zerit, and resulted in a mean recovery of active drug from solution of over 97%, confirming the accuracy of this dosing method. The contents of Stavir capsules, however, were extremely difficult to disperse in water despite prolonged agitation; consequently, the recovery of active drug from the solution was reduced. Conclusion. The accuracy of the off-label opened capsule dosing method for stavudine is acceptable. There is no need to instruct caregivers to include sediment in the aliquot given to the infant. However, studies that confirm adequate bioavailability and efficacy are needed. In addition, it is important to avoid supplying generic capsules the contents of which do not disperse easily in water, as this may lead to a significant reduction in the amount of active drug that a child receives.
- ItemEducation and training for medicines development, regulation, and clinical research in emerging countries(Frontiers Media, 2015) Kerpel-Fronius, Sandor; Rosenkranz, Bernd; Allen, Elizabeth; Bass, Rolf; Mainard, Jacques D.; Dodoo, Alex; Dubois, Dominique J.; Hela, Mandisa; Kern, Steven; Massud, Joao; Silva, Honorio; Whitty, JeremyThe aim of this satellite workshop held at the 17th World Congress of Basic and Clinical Pharmacology (WCP2014) was to discuss the needs, optimal methods and practical approaches for extending education and teaching of medicines development, regulation, and clinical research to Low and Middle Income Countries (LMICs). It was generally agreed that, for efficiently treating the rapidly growing number of patients suffering from non-communicable diseases, modern drug therapy has to become available more widely and with a shorter time lag in these countries. To achieve this goal many additional experts working in medicines development, regulation, and clinical research have to be trained in parallel. The competence-oriented educational programs designed within the framework of the European Innovative Medicine Initiative-PharmaTrain (IMI-PhT) project were developed with the purpose to cover these interconnected fields. In addition, the programs can be easily adapted to the various local needs, primarily due to their modular architecture and well defined learning outcomes. Furthermore, the program is accompanied by stringent quality assurance standards which are essential for providing internationally accepted certificates. Effective cooperation between international and local experts and organizations, the involvement of the industry, health care centers and governments is essential for successful education. The initiative should also support the development of professional networks able to manage complex health care strategies. In addition it should help establish cooperation between neighboring countries for jointly managing clinical trials, as well as complex regulatory and ethical issues.
- ItemHealth-related quality of life and its association with medication adherence in active pulmonary tuberculosis– a systematic review of global literature with focus on South Africa(BioMed Central, 2016-03-11) Kastien-Hilka, Tanja; Abulfathi, Ahmed; Rosenkranz, Bernd; Bennett, Bryan; Schwenkglenks, Matthias; Sinanovic, EdinaIntroduction: Tuberculosis (TB) is a leading cause of morbidity and mortality in South Africa. Clinical parameters are important objective outcomes in TB; however they often are not directly correlated with subjective well-being of the patient, but can be assessed using patient-reported outcome (PRO) measures. Health-related quality of life (HRQOL) is a specific PRO generally multi-dimensional in nature and includes physical, mental and social health domains. The inclusion of HRQOL PROs in trials and clinical practice can provide additional information beyondclinical and microbiological parameters. Furthermore, HRQOL may be associated with medication adherence. This review focuses on patient-reported HRQOL and its association with medication adherence in TB patients in South Africa. Methods: A comprehensive search strategy was developed focusing on the impact of TB on patient-reported HRQOL,the existence of a conceptual framework of TB-specific HRQOL, determinants of medication adherence and the association of HRQOL with medication adherence. Data were extracted from all identified articles and additional data extraction was performed by two independent reviewers with special focus on longitudinal studies in order to understand changes of HRQOL and adherence over time. Research gaps were identified with regard to patientreported HRQOL and medication adherence. Results: A total of 66 articles met the eligibility criteria. Ten HRQOL studies and one adherence study used a longitudinal design, none of these in South Africa. A variety of different generic and disease-specific HRQOL measures were identified in the articles. In South Africa four HRQOL and five adherence studies (non-longitudinal) were published. Similar factors (socio-demographic, socio-economic, disease-related, therapy-related and psycho-social aspects) affect HRQOL and adherence. Although standard TB treatment improved all health domains, psychological well-being and social functioning remained impaired in microbiologically cured patients after treatment. (Continued on next page)
- ItemHealth-related quality of life in South African patients with pulmonary tuberculosis(Public Library of Science, 2017) Kastien-Hilka, Tanja; Rosenkranz, Bernd; Sinanovic, Edina; Bennett, Bryan; Schwenkglenks, MatthiasBackground: The evaluation of patient-reported health-related quality of life (HRQOL) in pulmonary tuberculosis (TB) contributes to a comprehensive understanding of the burden associated with this disease. The aim of this study was to assess the overall impact of TB on the health status and on single health domains identified in the WHO definition of health, including physical, mental and social health aspects. Methods: Four instruments for HRQOL evaluation were applied in a longitudinal multicentre study during six-month standard TB treatment in South Africa. These included the generic SF-12 and EQ-5D-5L, the disease-specific St. George´s Respiratory Questionnaire (SGRQ) and the condition-specific Hospital Anxiety and Depression Scale (HADS). Statistical analysis included significance testing, univariable and multivariable analysis, and repeated measures ANOVA. Change over time in the physical component score (PCS) of SF-12 was defined as primary endpoint. A target sample size of 96 patients was estimated. Results: HRQOL of the study participants was impaired in all physical, mental and psycho-social health domains at treatment start. HRQOL improved significantly and in a clinically meaningful manner during the course of standard TB treatment, over the period of the study. The greatest improvement (95%) was observed in mental health. Younger patients with higher education and who were employed had a better HRQOL. Discussion: This study demonstrates the need for an integrative understanding of TB with HRQOL as core element to inform gaps in current TB management. Improvements in the management of TB following an integrative patient-centred approach will contribute towards meeting the United Nations Sustainable Development Goal 3 (SDG3) target and will support the End TB strategy of the WHO.
- ItemHow to evaluate health-related quality of life and its association with medication adherence in pulmonary tuberculosis – designing a prospective observational study in South Africa(Frontiers Media, 2016) Kastien-Hilka, Tanja; Rosenkranz, Bernd; Bennett, Bryan; Sinanovic, Edina; Schwenkglenks, MatthiasIntroduction: Health-related quality of life (HRQOL) has become an important measure to identify and shape effective and patient-relevant healthcare interventions innovations through outcomes. Adherence to tuberculosis (TB) treatment is a public health concern. The main objective of this research is to develop a study design for evaluation of HRQOL and its association with medication adherence in TB in South Africa. Methodology: A conceptual framework for HRQOL in TB has been developed to identify Patient-Reported Outcomes and Quality of Life Database (PROQOLID), (n.d.) measures for HRQOL and adherence and to generate an endpoint model. Two generic (SF-12 and EQ-5D-5L), one disease-specific (St. George’s Respiratory Questionnaire) and one condition-specific (Hospital Anxiety and Depression Scale) measure for HRQOL and Morisky Medication Adherence Scale for adherence assessment were identified. All measures are applied in a longitudinal multi-center study at five data collection time points during standard TB treatment. Statistical analysis includes multivariable analysis. Change over time in the physical component score of SF-12 is defined as primary endpoint. Sample size estimation based thereupon has led to a recruitment target of 96 patients. This study is on-going. Discussion: This is the first longitudinal study in South Africa which evaluates HRQOL and its association with medication adherence in TB in a comprehensive manner. Results will help to improve current treatment programs and medication adherence and will support the identification of sustainable health innovations in TB, determining the value of new products, and supporting decision making with regard to health policy and pricing.
- ItemIn vitro assessment of the interaction potential of ocimum basilicum (L.) extracts on CYP2B6, 3A4, and rifampicin metabolism(Frontiers Media, 2020-04-30) Kumar, Saneesh; Bouic, Patrick J.; Rosenkranz, BerndENGLISH ABSTRACT: Ocimum basilicum L. or basilicum is a common culinary herb, used as a traditional medicine for various medical conditions including HIV/AIDS and tuberculosis, in Africa. The objective of this study was to evaluate the effect of methanol, ethanol, aqueous and ethyl acetate extracts of the dried leaves and inflorescence of O. basilicum, on the activity of cytochrome P450 enzymes (CYPs) CYP2B6 and 3A4, as well as esterase-mediated metabolism of rifampicin to 25-O-desacetyl rifampicin (25ODESRIF). Human liver microsomes (HLM) were used to evaluate inhibition and CYP2B6/3A4 mRNA expression HepG2 assays were used to measure induction. Furthermore, the phytoconstituents likely involved in causing the observed effect were analyzed using biochemical tests and LC-MS. The aqueous and methanolic extracts showed reversible and time-dependent inhibition (TDI) of CYP2B6 with TDI-IC50s 33.35 μg/ml (IC50 shift-fold >1.5) and 4.93 μg/ml (IC50 shift-fold >7) respectively, while the methanolic and ethanolic extracts inhibited 25ODESRIF formation (IC50s 31 μg/ml, 8.94 μg/ml). In HepG2 assays, the methanolic and ethanolic extracts moderately induced CYP2B6, 3A4 mRNA with 38%-, 28%-fold shift, and 22%-, 44%-fold shift respectively. LC-MS full scans identified phenols rosmarinic acid [m/z 359 (M-H)-, approximately 2298 mg/L in aqueous extract] and caftaric acid along with flavones salvigenin [m/z 329 (M+H)+, approximately 1855 mg/L in ethanolic extract], eupatorin [m/z 345 (M+H)+, 668.772 mg/L in ethanolic extract], rutin [m/z 609 (M-H)-] and isoquercetin [m/z 463 (M-H)-] and other compounds—linalool [m/z 153 (M-H)-], hydroxyjasmonic acid [m/z 225 (M-H)-], eucommiol [m/z 187 (M-H)-] and trihydroxy octadecenoic acid [m/z 329 (M-H)-, 530 mg/L in ethanolic extract]. The putative gastrointestinal tract (GIT) concentration for all extracts was calculated as 2,400 μg/ml and hepatic circulation concentrations were estimated at 805.68 μg/ml for the aqueous extract, and 226.56 μg/ml for methanolic extract. Based on the putative GIT concentration, estimated hepatic circulation concentration [I] and inhibition constant Ki, the predicted percentile of inhibition in vivo was highest for the aqueous extract on CYP2B6 (96.7%). The observations indicated that O. basilicum extracts may have the potential to cause clinically relevant herb-drug interactions (HDI) with CYP2B6 and rifampicin metabolism in vivo, if sufficient hepatic concentrations are reached in humans.
- ItemInhibitory interactions of Aspalathus linearis (Rooibos) extracts and compounds, aspalathin and Z-2-(β-D-glucopyranosyloxy)-3-phenylpropenoic acid, on cytochromes metabolizing hypoglycemic and hypolipidemic drugs(MDPI, 2016-11-12) Patel, Oelfah; Muller, Christo; Joubert, Elizabeth; Louw, Johan; Rosenkranz, Bernd; Awortwe, CharlesRooibos extract, due to its glucose and lipid lowering effects, has potential as a nutraceutical for improvement of metabolic dysfunction. Potential herb-drug interactions as a result of the use of natural products are of increasing concern. Cytochrome P450 enzymes, CYP2C8, CYP2C9, and CYP3A4, are important in the metabolism of hypoglycemic drugs, such as thiazolidinediones (TZDs) and sulfonylureas, and hypocholesterolemic drugs, such as atorvastatin. This study investigated the effects of rooibos extracts, prepared from “unfermented” and “fermented” rooibos plant material and two of the major bioactive compounds, Z-2-(β-d-glucopyranosyloxy)-3-phenylpropenoic acid (PPAG) and aspalathin (ASP), on Vivid® recombinant CYP450 enzymes. Unfermented (GRT) and fermented (FRE) rooibos extracts inhibited the activity of CYP2C8 (7.69 ± 8.85 µg/mL and 8.93 ± 8.88 µg/mL, respectively) and CYP3A4 (31.33 ± 4.69 µg/mL and 51.44 ± 4.31 µg/mL, respectively) based on their respective IC50 concentrations. Both extracts dose- and time-dependently inhibited CYP2C8 activity, but only time-dependently inhibited CYP2C9. CYP3A4 showed concentration-dependent inhibition by ASP, GRT, and FRE at 25, 50, and 100 µg/mL concentrations. ASP, GRT, and FRE time-dependently inhibited CYP3A4 activity with GRT and FRE showing a more potent time-dependent inhibition, comparable to erythromycin. These findings suggest that herb-drug interactions may occur when nutraceuticals containing rooibos extracts are co-administered with hypoglycemic drugs such as TZDs, sulfonylureas, and dyslipidemic drug, atorvastatin.
- ItemAn overview of the evidence and mechanisms of herb-drug interactions(Frontiers, 2012-04-30) Fasinu, Pius S.; Bouic, Patrick J.; Rosenkranz, BerndDespite the lack of sufficient information on the safety of herbal products, their use as alternative and/or complementary medicine is globally popular. There is also an increasing interest in medicinal herbs as precursor for pharmacological actives. Of serious concern is the concurrent consumption of herbal products and conventional drugs. Herb–drug interaction (HDI) is the single most important clinical consequence of this practice. Using a structured assessment procedure, the evidence of HDI presents with varying degree of clinical significance. While the potential for HDI for a number of herbal products is inferred from non-human studies, certain HDIs are well established through human studies and documented case reports. Various mechanisms of pharmacokinetic HDI have been identified and include the alteration in the gastrointestinal functions with consequent effects on drug absorption; induction and inhibition of metabolic enzymes and transport proteins; and alteration of renal excretion of drugs and their metabolites. Due to the intrinsic pharmacologic properties of phytochemicals, pharmacodynamic HDIs are also known to occur. The effects could be synergistic, additive, and/or antagonistic. Poor reporting on the part of patients and the inability to promptly identify HDI by health providers are identified as major factors limiting the extensive compilation of clinically relevant HDIs. A general overview and the significance of pharmacokinetic and pharmacodynamic HDI are provided, detailing basic mechanism, and nature of evidence available. An increased level of awareness of HDI is necessary among health professionals and drug discovery scientists. With the increasing number of plant-sourced pharmacological actives, the potential for HDI should always be assessed in the non-clinical safety assessment phase of drug development process. More clinically relevant research is also required in this area as current information on HDI is insufficient for clinical applications.
- ItemThe potential of Hypoxis hemerocallidea for herb-drug interaction(Informa Healthcare, 2013) Fasinu, Pius S.; Gutmann, Heike; Schiller, Hilmar; Bouic, Patrick J.; Rosenkranz, BerndContext: Aqueous decoction of Hypoxis hemerocallidea Fisch. & C.A. Mey. (Hypoxidaceae) (Hypoxis) is widely consumed in Southern Africa by people living with HIV/AIDS, some of whom are on ARV and other medications. Objective: The aim of this study was to investigate the potential of the crude aqueous extracts of Hypoxis to inhibit major forms of CYP450 and transport proteins. Materials and methods: Corms of Hypoxis were water-extracted and incubated (in graded concentrations: 1–100 mg/mL) with human liver microsomes (20 min) to monitor the effects on phenacetin O-deethylation, coumarin 7-hydroxylation, bupropion hydroxylation, paclitaxel 6a-hydroxylation, diclofenac 40 -hydroxylation, S-mephenytoin 40 -hydroxylation, bufuralol 10 -hydroxylation, chlorzoxazone 6-hydroxylation, midazolam 10 -hydroxylation and testosterone 6b-hydroxylation as markers for the metabolic activities of CYP1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1 and 3A4/5, respectively. The generation of metabolites were monitored and quantified with the aid of LC-MS/MS. The potential of the extracts to inhibit human ATPbinding cassette transporter activity was assessed using recombinant MDCKII and LLC-PK1 cells over-expressing human breast cancer resistant protein and human P-glycoprotein , respectively (with Ko143 and cyclosporin A as positive controls). Similar assessment was performed with human organic anion transporting polypeptide (OATP1B1 and OATP1B3) using recombinant HEK293 cells over-expressing OATP1B1 and OATP1B3, respectively (with rifamycin and 10 mM atorvastatin as positive controls). Results: Extracts of Hypoxis inhibited the production of the metabolites of the substrates of the following enzymes (as compared to controls) with the indicated IC50 values (mg/mL): CYP1A2 (120.6), CYP2A6 (210.8), CYP2B6 (98.5), CYP2C8 (195.2), CYP2C9 (156) and CYP3A4/5 (185.4). The inhibition of the uptake activity of OATP1B1 and OATP1B3 were also observed with IC50 values of 93.4 and 244.8 mg/mL, respectively. Discussion: Extract concentrations higher than the estimated IC50 values are achievable in the gastrointestinal tract when traditional doses of Hypoxis are considered. This may have profound effects on presystemic metabolism of the drug substrates. If absorbed, systemic inhibition of metabolic enzymes/transporters by Hypoxis may be expected. Conclusion: The result suggests that there is the potential for HDI between Hypoxis and the substrates of the affected enzymes/transporters, if sufficient in vivo concentration of Hypoxis extracts is attained.
- ItemSnake bites, spider bites and scorpion stings(Health and Medical Publications Group (HMPG), 2012-10) Rosenkranz, BerndExposure of humans to natural toxins occurs via snake bites, spider bites and scorpion stings, or by plant or mushroom poisonings. According to the WHO (http://www.who.int/neglected_diseases/ diseases/snakebites/en/), envenoming is in fact one of the neglected tropical diseases and forms a particularly important public health problem in tropical and subtropical countries.
- ItemA Validated stable HPLC method for the simultaneous determination of rifampicin and 25-O-desacetyl rifampicin – evaluation of in vitro metabolism(Akademiai Kiado, 2017) Kumar, Saneesh; Bouic, Patrick J.; Rosenkranz, BerndA simple, efficient, and stable high-performance liquid chromatography (HPLC) separation method for a combination of rifampicin (RIF), its major metabolite 25-O-desacetyl rifampicin (25ODESRIF), and neostigmine (NEO) was developed and validated. The drugs individually, and in combination, were analyzed using a Waters Alliance 2695 HPLC coupled with 2996 photodiode array detector (PDA). Successful separation of combined drugs was achieved by gradient elution on a reverse-phase C-18 Phenomenex Luna column, using a mobile phase consisting of water and methanol at detection wavelength of 254 nm. The HPLC retention times were consistent at ±7.70 min, ±8.25 min, and ±10.70 min for RIF, 25ODESRIF, and NEO, respectively. The regression data for the calibration plots exhibited linear relationship (R 2 = 0.995) in the range of 0–200 μM for both RIF and 25ODESRIF, and the lower limit of detection (LLOD) and lower limit of quantification (LLOQ) were calculated at 5.86 μM and 17.75 μM for RIF and 7.78 μM and 23.57 μM for 25ODESRIF, respectively. The method was evaluated using in vitro human liver microsomes (HLMs) assays, and linearity was established for the 15, 30, 45, and 60 min incubations (R2 = 0.99). The formation of 25ODESRIF was characterized by hyperbolic kinetics (Km 48.23 μM, Vmax 1.233 pmol/min/mg protein, and CLint 0.026 μl/min/mg protein). The method was applied in HLM assays to understand the herb–drug interaction (HDI) potential of Althaea officinalis, a popular African herb consumed by tuberculosis (TB) patients, with RIF. None of the extracts of A. officinalis inhibited the esterase-mediated metabolism pathway of RIF, compared to the positive control nelfinavir (IC50 = 9.59 μM). The method provides a tool for quantifying RIF and 25ODESRIF in in vitro drug metabolism assays as well as investigating herb– and drug–drug interactions (DDIs).