Abstract
Patients receiving anti-retroviral drug treatment are sometimes simultaneously taking herbal remedies, which may result in pharmacokinetic herb-drug interactions. This study aimed to determine if pharmacokinetic interactions exist between selected commercially available herbal products (i.e., Linctagon Forte®, Viral Choice® and Canova®) and indinavir in terms of in vitro transport and metabolism. Bi-directional transport of indinavir was evaluated across Caco-2 cell monolayers in the presence and absence of the selected herbal products and verapamil (positive control). Metabolism of indinavir was determined in LS180 cells in the presence and absence of the selected herbal products as well as ketoconazole (positive control). The secretory transport of indinavir increased in a concentration dependent way in the presence of Linctagon Forte® and Viral Choice® when compared to that of indinavir alone. Canova® only slightly affected the efflux of indinavir compared to that of the control group. There was a pronounced inhibition of the metabolism of indinavir in LS180 cells over the entire concentration range for all the herbal products investigated in this study. These in vitro pharmacokinetic interactions indicate the selected herbal products may affect indinavir’s bioavailability, but the clinical significance needs to be confirmed with in vivo studies before final conclusions can be made.
Highlights
Human immunodeficiency virus (HIV) infection and acquired immune deficiency syndrome (AIDS) remains one of the biggest health problems that the world and sub-Saharan Africa, is facing
Inhibition of CYP3A4 may result in increased bioavailability of orally administered drugs with potentiation of adverse effects and possible toxicity, whereas induction thereof will increase metabolism of administered drugs resulting in reduced oral bioavailability and efficacy of drugs [3]
The current study investigated if in vitro pharmacokinetic interactions in terms of efflux and metabolism modulation exist between indinavir and three selected commercially available herbal products (i.e., Canova®, Linctagon Forte® and Viral Choice®) that are often used by patients for immune boosting effects, sometimes in conjunction with prescribed medication
Summary
Human immunodeficiency virus (HIV) infection and acquired immune deficiency syndrome (AIDS) remains one of the biggest health problems that the world and sub-Saharan Africa, is facing. Pharmacokinetic interactions caused by herbal products involve induction and/or inhibition of intestinal efflux proteins as well as intestinal and hepatic metabolising enzymes [3]. Its main physiological function is believed to provide protection against the onslaught of endogenous and exogenous compounds due to its ability to transport various structural dissimilar compounds out of the epithelial cells. This action of P-gp to extrude drug molecules from the epithelium back into the gastro-intestinal lumen may cause reduction in the absorption of a drug and results in decreased oral bioavailability thereof [5]. Inhibition of CYP3A4 may result in increased bioavailability of orally administered drugs with potentiation of adverse effects and possible toxicity, whereas induction thereof will increase metabolism of administered drugs resulting in reduced oral bioavailability and efficacy of drugs [3]
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