• What Is Atazanavir?
• Who Should Take It?
• What About Drug Resistance?
• How Is It Taken?
• What Are the Side Effects?
• How Does It React With Other Drugs?

What Is Atazanavir?

Atazanavir, also called Reyataz^®, is a drug used as part of antiretroviral therapy (ART). It used to be called BMS-232632. Atazanavir is a protease inhibitor manufactured by Bristol-Myers Squibb. Atazanavir was approved by the FDA in 2003.

Protease inhibitors prevent the protease enzyme from working. HIV protease acts like a chemical scissors. It cuts the raw material for HIV into specific pieces needed to build a new virus. Protease inhibitors "gum up" these scissors.

Who Should Take It?

Atazanavir was approved in 2003 as an antiretroviral drug (ARV) for people with HIV infection.It should not be given to patients younger than 3 months. There are no recommendations for children younger than 6 years of age. Doses for children are based on their weight. They can be found at www.aidsinfo.nih.gov/

There are no absolute rules about when to start ART. You and your health care provider should consider your CD4 cell count, your viral load, any symptoms you are having and your attitude about taking ART. Fact Sheet 404 has more information about guidelines for the use of ART.

If you take atazanavir with other ARVs, you can reduce your viral load to extremely low levels, and increase your CD4 cell counts. This should mean staying healthier longer. Although other protease inhibitors lead to increases in blood fats, atazanavir does not. If you have high cholesterol or triglycerides, or other risk factors for heart disease, your physician might want you to use atazanavir.

What About Drug Resistance?

Many new copies of HIV are mutations. They are slightly different from the original virus. Some mutations can keep multiplying even when you are taking an ARV. When this happens, the drug will stop working. This is called "developing resistance" to the drug. See Fact Sheet 126 for more information on resistance.

Sometimes, if your virus develops resistance to one ARV, it will also have resistance to other ARVs. This is called "cross-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 ARVs according to instructions, on schedule, and not to skip or reduce doses.

How Is It Taken?

Atazanavir is taken once a day by mouth as a capsule. For patients just starting ART, the normal dose is 400 mg 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, 200 mg and 300 mg. Store atazanavir at room temperature, protected from moisture. Keep it in a tightly sealed container.

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

What Are the 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. That is, triglyceride, cholesterol and glucose levels stay close to normal, unlike with other protease inhibitors. 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 health care provider 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.

How Does It React With Other Drugs?

Atazanavir can interact with other drugs or supplements that you are taking. These interactions can change the amount of each drug in your bloodstream and cause an under- or overdose. New interactions are being identified all the time.

Drugs to watch out for include other ARVs, drugs to treat tuberculosis (see Fact Sheet 518), for erectile dysfunction (such as Viagra), for heart rhythm (antiarrhythmics), and for migraine headaches. Interactions are also possible with several antihistamines (allergy medications), sedatives, drugs to lower cholesterol, and anti-fungal drugs. Make sure that your health care provider knows about ALL drugs and supplements you are taking.

• If you are taking atazanavir and the original buffered form of ddI, take ddI two hours before or after atazanavir.
• Atazanavir should not be taken with indinavir (Crixivan) due to the increased risk of jaundice.
• Amprenavir levels are increased by atazanavir.
• Efavirenz (Sustiva) and tenofovir (Viread) lower blood levels of atazanavir.
• Atazanavir does not seem to change blood levels of birth control pills.
• There is no interaction between atazanavir and methadone.
• Watch for signs of excessive sedation if you take atazanavir with buprenorphine.
• Guidelines for taking antacids with atazanavir are complicated. They were updated in 2008. Be sure your health care provider knows if you are taking Prilosec, Zantac, Pepsid or other antacids.
• The herb St. John's Wort (see Fact Sheet 729) lowers the blood levels of some protease inhibitors. Do not take it with atazanavir.