atazanavir, Reyataz (cont.)

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Medical and Pharmacy Editor:

Atazanavir is best absorbed under acidic conditions. Therefore, medications that decrease stomach acidity could reduce the absorption of atazanavir. Drugs that decrease stomach acidity include antacids, proton pump inhibitors such as omeprazole (Prilosec), lansoprazole (Prevacid), pantoprazole (Protonix), rabeprazole (Aciphex) esomeprazole (Nexium); H2-receptor antagonists such as cimetidine (Tagamet), ranitidine (Zantac), famotidine (Pepcid), nizatidine (Axid); and buffered drugs such as didanosine (Videx). Individuals who are taking antacids or didanosine should take their atazanavir two hours before or one hour after the didanosine or antacid. Proton pump inhibitors should not be combined with atazanavir in previously treated patients. For treatment naive patients the dose of proton pump inhibitor should not exceed the equivalent of omeprazole 20 mg and must be given 12 hours before administration of atazanavir. The dose of H2-antagonists should not exceed the equivalent of 40 mg famotidine twice daily and atazanavir should be administered 2 hours before or 10 hours after administration of the H2-antagonists.

Atazanavir increases the effect of warfarin (Coumadin). Therefore the effect of warfarin should be monitored more frequently and doses should be modified accordingly.

Combining amiodarone (Cordarone), lidocaine, quinidine, or bepridil (Vascor) with atazanavir may cause dangerous abnormal heart rhythms.

Atazanavir increases blood levels of PDE5 inhibitors such as sildenafil (Viagra, Revatio), tadalafil (Adcirca, Cialis), and vardenafil (Levitra). Atazanavir should not be combined with Revatio (sildenafil used for treating pulmonary hypertension). It should be used with caution with reduced doses of the other PDE5 inhibitors.

PREGNANCY: Atazanavir has not been adequately studied in pregnant women.

NURSING MOTHERS: Atazanavir has not been adequately studied in nursing mothers. Scientific experts advise HIV-infected mothers not to breastfeed because of the risk of transmitting HIV to the infant.

SIDE EFFECTS: The most common side effects of atazanavir are rash, nausea, diarrhea, vomiting, headache, insomnia, dizziness, muscle pain, depression, fever, and abdominal pain. Atazanavir may cause jaundice by increasing bilirubin in the blood. Some patients also may see an increase in blood glucose levels or an increase or redistribution of body fat. Changes in body fat may include increased fat in the upper back and neck (buffalo hump), trunk and breasts. In a small number of patients atazanavir may decrease heart rate. In a small number of patients a serious condition called lactic acidosis--a build up of acid in the blood--may occur. Symptoms of lactic acidosis include persistent nausea, vomiting, weakness and trouble breathing. Individuals with bleeding disorders may bleed more when taking atazanavir.

Reference: FDA Prescribing Information

Last Editorial Review: 9/5/2012

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