WHAT IS ATAZANAVIR? 

Atazanavir, also called Reyataz,  is a drug  used as part of antiretroviral therapy (ART).   Atazanavir is a protease inhibitor manufactured  by Bristol-Myers Squibb. Atazanavir was approved by  the FDA  in 2003.  Generic versions have been tentatively approved under PEPFAR (see fact sheet 475.) 

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 can  be given to children over 6 years old, and adults.   

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. 

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. 

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 with food as capsules. For adults just starting ART, the normal dose is 300 mg plus 100 mg of ritonavir, once a day. 

Patients who cannot tolerate ritonavir should take 400 mg of atazanavir. However, this is not recommended  for patients who have taken  other HIV medications and experienced treatment failure. 

Dosing  for children at least 6 years old is based on their weight and prior treatment history. 

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. 

WHAT ARE THE SIDE EFFECTS? 

Atazanavir can cause high levels  of bilirubin, nausea, headache, rash, stomach pain, vomiting, diarrhea, tingling in hands or feet, and depression. Atazanavir may cause changes in heart rhythm. Tell  your health care provider if you feel dizzy while taking atazanavir. 

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 usually not the case for people taking atazanavir because the drug blocks normal removal of bilirubin. 

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 clear if atazanavir is associated with lower rates of body shape changes (lipodystrophy.) 

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, especially efavirenz or nevirapine), 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. 
• Atazanavir can increase levels of hormones contained in birth control pills. Other methods of contraception are recommended. 
• Tenofovir (Viread) lowers blood levels of atazanavir. 
• There is no interaction between atazanavir and methadone. 
• Watch for signs of excessive sedation if you take atazanavir with buprenorphine. 
• Do not combine atazanavir eith midazolam (Versed.) 
• 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  lowers the blood levels of some protease inhibitors. Do not take it with atazanavir.