Effect of Concurrent Administration of Herbs on the Pharmacokinetics of Drugs: A Review

Herbal medicines are currently in high demand, and their popularity is steadily increasing as an alternative medicine. This is as a result of their perceived effectiveness, fewer side effects and relatively low cost. They are being used simultaneously with therapeutic drugs for the treatment and management of numerous medical conditions, but due to the complex mixture of bioactive constituents they are capable of affecting the pharmacokinetics and pharmacodynamics of conventional drugs when administered concurrently. Of serious concern is the concurrent consumption of herbal products and conventional drugs. Herb–drug inter-action (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. This herb-drug interactions (HDIs) may lead to modifications in plasma drug levels resulting in therapeutic failure of the drug or, alternatively, it may cause drug-induced toxicity. The main routes proposed for HDIs include cytochrome P450 (CYP450)-mediated inhibition or induction and transport and flow proteins. In our review, some herbal medicines used for the treatment of various diseases were highlighted and case reports of their pharmacokinetics and pharmacodynamics herb-drug interactions were analyzed. Therefore, this review can be a quick reference tool for physicians, pharmacists and other healthcare professionals involved in therapy, and counseling towards appropriate use of drugs to maximize clinical outcomes.