Atazanavir

POZ IRELAND

gpi@poz.iol.ie

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ATAZANAVIR

Updated October 2004

WHAT IS ATAZANAVIR?

Atazanavir, also called Reyataz® is a protease inhibitor. It has been approved for use against HIV.

RESISTANCE

Atazanavir provides blood levels that are high enough to control HIV that has already developed some resistance to other protease inhibitors.

Resistance can develop quickly. It is very important to take antiviral medications according to instructions, on schedule, and not to skip or reduce doses.

DOSAGE

Atazanavir is taken by mouth as a capsule. Each capsule contains 200 milligrams (mg) of atazanavir. The normal dose is two capsules once a day, taken with food.

For patients who have taken protease inhibitors before, the dose is 300 mg plus 100 mg of ritonavir, also taken once a day with food. Atazanavir is available in capsules of 100 mg, 150 mg and 200 mg. Store atazanavir at room temperature, protected from moisture. Keep it in a tightly sealed container.

Many doctors combine atazanavir with a small "booster" dose of ritonavir. This is especially true if atazanavir is not the patient's first protease inhibitor.

SIDE EFFECTS

In clinical trials, atazanavir caused very high levels of bilirubin in over 30% of patients who took it. Bilirubin is produced by the liver when old red blood cells are broken down. High levels of bilirubin can cause yellow skin or eyes. This is called jaundice. About 10% of patients using atazanavir got jaundice.

High bilirubin levels can be a sign of liver damage. However, this is not the case for people taking atazanavir. The drug blocks normal removal of bilirubin. Less than 1% of patients stopped taking atazanavir due to high bilirubin levels. Bilirubin levels returned to normal within a few days in people who stopped taking atazanavir.

Atazanavir does not seem to increase the levels of fat or sugar in the blood. This could be an advantage for people who want to reduce their long-term risk of heart disease. It is not yet known if atazanavir is associated with lower rates of body shape changes (lipodystrophy).

Atazanavir may cause changes in heart rhythm. Tell your doctor if you feel dizzy while taking atazanavir. Other side effects may include nausea, headache, rash, stomach pain, vomiting, diarrhea, tingling in hands or feet and depression.

DRUG INTERACTIONS

Atazanavir is broken down by the liver and can interact with other drugs that also use the liver. Combining these drugs can change the amount of each drug in your bloodstream and cause an under- or overdose. Drugs to watch out for include Viagra, several antihistamines, sedatives, drugs to lower cholesterol and anti-fungal drugs. Make sure that your doctor knows about ALL drugs you are taking.

If you are taking atazanavir and the original buffered form of ddI, take ddI two hours before or after atazanavir. You should also take atazanavir one hour apart from antacids.

Atazanavir should not be taken with indinavir (Crixivan) due to the increased risk of jaundice.

Amprenavir levels are increased by atazanavir. Lower amprenavir doses may be appropriate.

Efavirenz (Sustiva) and tenofovir (Viread) lower blood levels of atazanavir. People taking atazanavir with either of these drugs need to change the dose of atazanavir and add a small dose of ritonavir.

Atazanavir does not seem to change blood levels of birth control pills.

No information is available on interactions between atazanavir and methadone.

The herb St. John's Wort lowers the blood levels of some protease inhibitors. Tell your doctor about any herbs or other supplements that you use.