AUC: ↓ 52% (↓ 33 til ↓ 66) Cmax: ↓ 45% (↓ 25 til ↓ 59) (CYP3A4- induktion) I en undersøgelse med HIV- inficerede stofmisbrugere, resulterede samtidig administration af efavirenz og methadon i et fald i methadons plasmakoncentrationer og abstinenssymptomer.
AUC: ↓ 52% (↓ 33 to ↓ 66) Cmax: ↓ 45% (↓ 25 to ↓ 59) (CYP3A4 induction) In a study of HIV infected intravenous drug users, co-administration of efavirenz with methadone resulted in decreased plasma levels of methadone and signs of opiate withdrawal.