Protease inhibitors Hormonal contraceptives

Rifampin is known to induce the hepatic microsomal enzymes that metabolize various drugs such as acetaminophen, oral anticoagulants, barbiturates, benzodiazepines, beta blockers, chloramphenicol, clofibrate, oral contraceptives, corticosteroids, cyclosporine, disopyramide, estrogens, hydantoins, mexiletine, quinidine, sulfones, sulfonylureas, theophyllines, tocainide, verapamil, digoxin, enalapril, morphine, nifedipine, ondansetron, progestins, protease inhibitors, buspirone, delavirdine, doxycycline, fluoroquinolones, losartan, macrolides, sulfonylureas, tacrolimus, thyroid hormones, TCAs, zolpidem, zidovudine, and ketoconazole. The therapeutic effects of these drugs may be decreased. 

Drugs That Interfere with Hormonal Contraceptives Concomitant use of HIV-protease inhibitors, griseofulvin, modafinil, penicillins, rifampin, rifabutin, phenytoin, carbamazepine, or certain herbal supplements such as St. John s wort with hormonal contraceptive agents may reduce the effectiveness of the contraception and up to one month after discontinuation of these concomitant therapies. Therefore, women requiring treatment with one or more of these drugs must use two other effective or highly effective methods of contraception or abstain from heterosexual sexual contact while taking thalidomide... 

Rifampin s potent induction of hepatic enzymes, especially cytochrome P450 (CYP) 3A4, may enhance the ehmination of many other drugs, most notably the protease inhibitors used to treat HIV (Table 110-7). HIV-positive patients may beneht from the use of rifabutin instead of rifampin (see below). ° Also, women who use oral contraceptives must use another form of contraception during therapy because increased clearance of the hormones may lead to unexpected pregnancies. Patient records should be reviewed for potential drug interactions before dispensing rifampin. Rifampin may turn urine and other secretions orange-red and may permanently stain some types of contact lenses. 

Vogler MA, Patterson K, Kamemoto L, Park J-G, Watts H, Aweeka F, KUngman KL, Cohn SE. Contraceptive efficacy of oral and transdermal hormones when co-administered with protease inhibitors in HIV-l-infected women. Pharmacokinetic results of ACTG trial A5188. J Acquir Immune Defic Dis 2010 55 473-82. 

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