Browsing by Author "Wonkam, Ambroise"

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    Inhibition of CYP2B6 by medicinal plant extracts : implication for use of efavirenz and nevirapine-based highly active anti-retroviral therapy (HAART) in resource-limited settings
    (MDPI, 2016-02-16) Thomford, Nicholas E.; Awortwe, Charles; Dzobo, Kevin; Adu, Faustina; Chopera, Denis; Wonkam, Ambroise; Skelton, Michelle; Blackhurst, Dee; Dandara, Collet
    Highly active antiretroviral therapy (HAART) has greatly improved health parameters of HIV infected individuals. However, there are several challenges associated with the chronic nature of HAART administration. For populations in health transition, dual use of medicinal plant extracts and conventional medicine poses a significant challenge. There is need to evaluate interactions between commonly used medicinal plant extracts and antiretroviral drugs used against HIV/AIDS. Efavirenz (EFV) and nevirapine (NVP) are the major components of HAART both metabolized by CYP2B6, an enzyme that can potentially be inhibited or induced by compounds found in medicinal plant extracts. The purpose of this study was to evaluate the effects of extracts of selected commonly used medicinal plants on CYP2B6 enzyme activity. Recombinant human CYP2B6 was used to evaluate inhibition, allowing the assessment of herb-drug interactions (HDI) of medicinal plants Hyptis suaveolens, Myrothamnus flabellifolius, Launaea taraxacifolia, Boerhavia diffusa and Newbouldia laevis. The potential of these medicinal extracts to cause HDI was ranked accordingly for reversible inhibition and also classified as potential time-dependent inhibitor (TDI) candidates. The most potent inhibitor for CYP2B6 was Hyptis suaveolens extract (IC50 = 19.09 ± 1.16 µg/mL), followed by Myrothamnus flabellifolius extract (IC50 = 23.66 ± 4.86 µg/mL), Launaea taraxacifolia extract (IC50 = 33.87 ± 1.54 µg/mL), and Boerhavia diffusa extract (IC50 = 34.93 ± 1.06 µg/mL). Newbouldia laevis extract, however, exhibited weak inhibitory effects (IC50 = 100 ± 8.71 µg/mL) on CYP2B6. Launaea taraxacifolia exhibited a TDI (3.17) effect on CYP2B6 and showed a high concentration of known CYP450 inhibitory phenolic compounds, chlorogenic acid and caffeic acid. The implication for these observations is that drugs that are metabolized by CYP2B6 when co-administered with these herbal medicines and when adequate amounts of the extracts reach the liver, there is a high likelihood of standard doses affecting drug plasma concentrations which could lead to toxicity.
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    Low hepatitis B vaccine uptake among surgical residents in Cameroon
    (BioMed Central, 2014-03) Noubiap, Jean Jacques N.; Nansseu, Jobert Richie N.; Kengne, Karen K.; Wonkam, Ambroise; Wiysonge, Charles S.
    Background: Hepatitis B virus (HBV) infection is one of the most serious occupational hazards faced by healthcare workers. Surgical personnel are particularly at risk. HBV infection is preventable by vaccination, but no previous study has assessed HBV vaccination coverage among healthcare workers in Cameroon. We assessed knowledge of risk factors of HBV infection, awareness of HBV vaccine, and vaccination status of surgical residents in Cameroon. Methods A structured pretested questionnaire was administered to 49 of the 70 surgical residents in Cameroon during the 2011–2012 academic year. Results Since the beginning of their residency program, 28 (57.1%) had had at least one accidental exposure to blood, with a median of 2 (range 1 to 25) exposures. Most of them had a good knowledge of risk factors for HBV infection. Although 98.0% (n = 48) were aware of the HBV vaccine, and 89.8% (n = 44) knew that they were at high risk of infection, only 24.5% (n = 12) had received a full course of at least three doses of the vaccine. In addition, only 33.3% (4/12) underwent post-vaccination testing to confirm a good immunological response (and thus effective protection against HBV infection). Among the 53.1% (n = 28) who had never had any dose of HBV vaccine, the main reasons for not being vaccinated were lack of time (38.5%), lack of money to pay for vaccine (23.1%), and lack of sufficient information on the vaccine (19.2%). Only 20.4% (n = 10) had been sensitized by their training institutions about the importance of HBV vaccination. Conclusion There is a low HBV vaccine uptake among surgical residents in Cameroon. As part of occupational safety measures, complete HBV vaccination should be strongly recommended and offered to surgical trainees before the beginning of their training program.