Atazanavir × Omeprazole

Atazanavir dissolves and is absorbed less well when stomach acidity falls, and omeprazole suppresses acid secretion. Omeprazole 40 mg daily cut exposure to ritonavir-boosted atazanavir by 75%, and raising atazanavir to 400 mg did not make up for it. Without ritonavir, exposure fell by 94%. As a result, HIV treatment may lose virologic response and the virus may develop resistance.

No outward signs; the problem shows up in lab tests: HIV viral load rises on treatment, and the virus may become resistant to atazanavir.

The combination is not recommended (omeprazole label; atazanavir label, European Medicines Agency (EMA)). If a proton pump inhibitor cannot be avoided, raise atazanavir to 400 mg with ritonavir 100 mg, keep omeprazole at no more than 20 mg a day and closely monitor the response to treatment, mainly viral load (omeprazole label; atazanavir label, EMA). Taking the drugs 12 hours apart does not prevent the drop in atazanavir levels (atazanavir label, EMA). For atazanavir without ritonavir, the label also advises against proton pump inhibitors (atazanavir label, EMA). The US Food and Drug Administration (FDA) does not recommend the combination in treatment-experienced patients; in treatment-naive patients it allows no more than omeprazole 20 mg taken about 12 hours before atazanavir 300 mg with ritonavir 100 mg (atazanavir FDA label). If acid suppression is needed, the atazanavir label allows H2-receptor antagonists with a dose limit: with atazanavir 300 mg plus ritonavir 100 mg and no tenofovir, no more than the equivalent of famotidine 20 mg twice daily (atazanavir label, EMA).