August 22, 2008

New Drug Interaction Information With Reyataz

The U.S. Food and Drug Administration (FDA) issued new instructions on potential drug interactions between the protease inhibitor Reyataz (atazanavir) and several other types of medications, including antiretroviral drugs, hormonal contraceptives and stomach acid reducers.

The FDA now recommends not using Reyataz with Viramune (nevirapine), whether or not Reyataz blood levels are boosted with low dose Norvir (ritonavir). This is because Viramune can significantly lower Reyataz blood levels, while Reyataz increases Viramune blood levels.

Another similar drug, efavirenz (found in Sustiva and Atripla), may be combined with Reyataz. However, the recommended daily dose of Reyataz is now 400 mg, and it must be combined with 100 mg of Norvir. The efavirenz dose remains 600 mg once daily at bedtime and on an empty stomach.

The FDA also issued new recommendations about using Reyataz with oral contraceptives, depending on whether or not the Reyataz is being boosted with Norvir. If Reyataz is used without Norvir, women should not take an oral contraceptive that contains more than 30 mcg of ethinyl estradiol. If Reyataz is combined with Norvir, then the birth control pill should contain at least 35 mcg of ethinyl estradiol.

Other types of hormonal contraceptives—such as the contraceptive patch, the contraceptive vaginal ring, injected contraceptives and oral contraceptives containing progestagens other than norethindrone or norgestimate or less than 25 mcg of ethinyl estradiol—have not been studied, and other methods of contraception are recommended.

Finally, another important update includes the use of Reyataz with stomach acid reducers known as H2-receptor antagonists (for instance Pepcid). Some people cannot tolerate Norvir and do not use it with Reyataz. These individuals can now also take an H2-receptor antagonist, provided that the Reyataz is taken at least two hours before or 10 hours after the dose of the H2-receptor antagonist.

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