Rifampin use can result in cytochrome P450 (CYP)-mediated drug-drug interactions with a wide set of drugs–in particular those metabolized by CYP2B6, CYP3A4/5, and CYP2A6. One common drug combination is the use of efavirenz, as part of HIV therapy, at the same time as rifampin for TB. The gene discussed is CYP3A4; the disease is tuberculosis.