Herb-drug interaction studies of herbs used in treatment of cardiovascular disorders-A narrative review of preclinical and clinical studies.

About 70% of the world population is currently using medicinal herbs as complementary or alternative medicine, which is increasing at a tremendous pace in both developed and developing countries in the last two decades (World Health Organization Medicines Strategy 2002-2005). This increase in consumer demand of medicinal herbs continues despite the rarity of scientific data to establish their safety and efficacy profile. Its popularity is also attributed to several factors, including easy availability, cost effectiveness leading to better purchasing power and general perception that they are safe. Herbs are often administered concomitantly with therapeutic drugs for the treatment of major ailments, raising the potential for herb-drug interactions (HDIs). The major pathways postulated for HDIs involves the cytochrome P450 (CYP450)-mediated inhibition or induction and transport and efflux proteins. In our review, we highlight frequently used herbal medicines for the treatment of cardiovascular disorders (CVD), their established HDIs studied using in vitro tools and in vivo pharmacokinetic and pharmacodynamic assays and case reports. Herbs have been divided into different sections on the basis of availability of HDI data in relevance to cardiovascular drugs: herbs reported to interact with cardiac drugs, herbs yet to be reported for interaction with drugs of any class and herbs reported to interact with drugs of other therapeutic category but not with cardiac drugs. The amount of active phytoconstituents present in the selected herbs and their extent of bioavailability are also mentioned. This review can serve as a quick reference database for physicians and health care professionals involved in CVD treatment, aimed at maximizing clinical outcomes with reduction in adverse and toxic effects.