Concomitant use of herbs with drugs may result in herb-drug interactions through various pharmacokinetic and pharmacodynamic mechanisms [
1,
2]. The risk of interaction increases with the number of co-administered agents. As a result, HIV patients in developing countries are at high risk of herb-drug interactions because of the widespread self-directed herbal medicine use; and the polypharmacy associated with HIV treatment [
3].
A growing number of studies are being conducted to evaluate the pharmacokinetic effects of herbs on drugs when taken together. However, the majority of studies use preclinical in vitro and animal models, which generate data that often do not translate to a clinical effect [
4,
5]. In addition, currently available data are skewed towards Chinese and Western herbs. Given the high prevalence of herbal medicine use and the rapid scaling up of treatment for HIV infection in developing countries, rigorous clinical studies are urgently required to assess the effects of commonly used herbal medicines on antiretroviral drugs. This will provide evidence to accurately guide herbal medicine use among HIV-infected people who choose to take herbs and drugs together.
In developing countries, the leaf powder of
Moringa oleifera Lam. is commonly used as a medicinal herb, rather than food as is the case in Asian populations. It is often taken as a supplement by HIV-infected people to enhance immunity and manage opportunistic infections [
6,
7]. In-vitro data suggest that moringa inhibits cytochrome P450 (CYP) 3A4, 1A2 and 2D6 activity which could potentially lead to metabolic interactions with antiretroviral drugs metabolized via the same pathways [
5,
8,
9]. The non-nucleoside reverse transcriptase inhibitor nevirapine (200 mg twice daily) is widely used as a component of first line antiretroviral therapy in many developing countries. It is metabolized mainly by CYP3A4 and CYP2B6 and to a lesser extent CYP3A5, CYP2C9, and CYP2D6 [
10,
11]. Previous studies have demonstrated that concomitant administration of fluconazole, a potent inhibitor of CYPs, results in markedly increased trough plasma nevirapine concentrations when compared to the administration of nevirapine alone [
12]. Concomitant dosing with the herb St. John’s wort, a CYP3A4 and P-glycoprotein inducer, reduced exposure to nevirapine [
13]. Such interactions with CYP inhibitors or inducers could potentially increase toxicity [
11] or reduce efficacy, respectively. Prior to this study, it was not known whether th
e in vitro inhibition potential of
Moringa oleifera Lam. is of clinical significance when co-administered with nevirapine. It was hypothesized that inhibition of CYP3A4 by
M. oleifera leaf powder may result in a clinically significant increase in nevirapine exposure. This study was conducted to assess the effect of 14 days
Moringa oleifera leaf powder supplementation on the steady-state pharmacokinetics of nevirapine in HIV-infected patients.