Introduction/Aim. Herbs have been a vital renewable source of medicine throughout human history as a large proportion of the global population still depends on them for their health benefits. The increasing popularity of herbal supplements has raised an obvious concern about the overall safety and potential interaction with other drugs in situ. The intent was to spur future research on herb-drug interactions as well as the mechanisms of interaction to understand the consequences of such interactions.
Methods. The review was conducted by a systematic search of relevant literature using the databases of Google Scholar, Science Direct, Mendeley, Scopus, and PubMed. Publications written in English were used. Many herbal products are reported to exhibit herb-drug interaction with known orthodox medicines. The inhibition-induction mechanism triggers chain reactions which often result in reduced drug bioavailability, toxicities, or undesirable side effects. Some herbal phytoconstituents reportedly bind CYP2C9, CYP2C19, CYP2E1, and CYP3A1 among numerous others temporarily or irreversibly.
Conclusion. The study was concluded by reiterating the imperativeness to routinely and regularly inform both physicians and patients of the inherent dangers such as reduced efficacy and increased toxicities associated with herb-drug interactions (HDI). Herb users should be regularly advised on the appropriate use of herbal supplements to avoid the risk of adverse drug interactions during co-administrations or in combination therapies. As both synergistic and antagonistic effects could be observed in HDI, further preclinical and clinical empirical studies are required to underscore the mechanism and extent of HDI.

 Keywords: herb-drug interaction, enzymes, pharmacokinetic interaction, traditional medicine, cytochrome P450

Corresponding author:
Mary O. Ologe
e-mail: funmiologe@yahoo.com