Atazanavir: Uses, Dosing, Side Effects & Drug Interactions

Atazanavir is an HIV protease inhibitor used to keep viral load low and protect the immune system. It’s commonly given with a booster—ritonavir or cobicistat—to improve levels in the body. People often prefer atazanavir because it’s taken once daily and tends to raise cholesterol less than older protease inhibitors.

How to take atazanavir matters. Take it with food to boost absorption. The usual adult dose is 300 mg once daily with ritonavir 100 mg or with cobicistat 150 mg as the booster. If you miss a dose, take it as soon as you remember unless it’s close to your next scheduled dose. Never double up without talking to your provider.

Interactions to watch for

Atazanavir needs acid to be absorbed, so antacids, H2 blockers, and proton pump inhibitors (PPIs) can cut its effectiveness. Avoid PPIs if possible. If you must use an H2 blocker, follow your doctor’s guidance on timing and dose. Antacids should be taken at least two hours before or one hour after atazanavir. Also watch out for medicines that change heart rhythm or interact with liver enzymes—statins like simvastatin are usually avoided with protease inhibitors. Tell your clinician about all prescriptions, over-the-counter drugs, and herbal products like St. John’s wort, which can lower atazanavir levels and cause treatment failure.

Common side effects and monitoring

The most common side effects are nausea, headache, and missed taste. Atazanavir can also raise bilirubin, which may cause a harmless yellowing of the skin or eyes. Your doctor will check bilirubin and liver tests while you’re on treatment. It can also affect the heart’s electrical conduction in some people, so tell your clinician if you have fainting, dizziness, or an irregular heartbeat.

Special situations matter. For people on methadone, atazanavir can sometimes lower methadone levels and cause withdrawal. For pregnant people, dosing and choice of booster may change; talk to a clinician experienced in HIV care. Kidney stones are rare but possible. If you have severe liver disease, atazanavir may not be recommended or will need close monitoring.

Practical tips: take atazanavir with a meal, carry an updated medication list, and avoid over-the-counter acid reducers without checking first. Don’t stop therapy suddenly—resistance can develop quickly. If you notice yellowing of the eyes, new irregular heartbeats, or persistent stomach pain, seek medical advice right away.

Want more details or patient-friendly guides? Ask your HIV clinic or pharmacist for a one-page printout about how to use atazanavir safely. They can help with dose timing, drug checks, and what tests you need during treatment.

If you travel, carry extra medicine and a copy of your prescription. Store atazanavir at room temperature away from moisture. Some people ask about switching off protease inhibitors; decisions depend on resistance tests and past treatment. If side effects interfere with daily life, your clinic can switch regimens safely. Use reliable sources like your clinic, pharmacists, or trusted HIV organizations for up-to-date advice. Keep an open line with your care team. Bring medication list to every appointment and ask about labs.