['The gut microbiome, an aggregate genome of trillions of microorganisms residing in the human gastrointestinal tract, is now known to play a critical role in human health and predisposition to disease. It is also involved in the biotransformation of xenobiotics and several recent studies have shown that the gut microbiota can affect the pharmacokinetics of orally taken drugs with implications for their oral bioavailability.', 'Review of Pubmed, Web of Science and Science Direct databases for the years 1957-2016.'] Does human gut microbiota play a role in the metabolism of drugs?