What medications can interact with probiotics?

Probiotics are generally safe and not known to interact with many medications -- but they are regulated as a food rather than a medication, so study has not been as stringent as it would be for a drug. There is concern that antibiotics taken at the same time as bacteria-based probiotics would kill the beneficial bacteria in the latter; also, people taking immunosuppressants may be in danger of illness from the active bacteria in most probiotics. An animal study also showed that the activity of drugs that are substrates of hepatic drug-metabolizing enzymes could be affected by probiotics, but this has not yet been confirmed in human studies.