Therapy-naïve patients: 300 mg/day PO with 100 mg ritonavir once daily; if unable to tolerate ritonavir, 400 mg PO once daily can be used. Taken with food. If taken with didanosine, give atazanavir with food 2 hr before or 1 hr after the didanosine. If taken with efavirenz, 400 mg/day PO atazanavir, and 100 mg ritonavir with food and 600 mg efavirenz as a single daily dose on an empty stomach, preferably at bedtime. Atazanavir should not be used with efavirenz without ritonavir. If taken with tenofovir, 300 mg tenofovir PO with 300 mg atazanavir PO and 100 mg ritonavir PO once daily with food.

Therapy-experienced patients: 300 mg/day PO with 100 mg ritonavir PO taken with food.

Concomitant therapy: With histamine-2 (H₂) receptor antagonists, do not exceed equivalent of 40 mg famotidine bid (for therapy-naïve patients) or 20 mg famotidine bid (for therapy-experienced patients); administer 300 mg atazanavir with 100 mg ritonavir simultaneously with first dose of H₂-receptor antagonist. Administer second dose of H₂-receptor antagonist 10 hr later. With proton pump inhibitors, do not exceed equivalent of 20 mg omeprazole. Administer 12 hr prior to atazanavir for therapy-naïve patients. Do not use proton pump inhibitors in therapy-experienced patients.