Macrolides Hormonal contraceptives

The macrolides clarithromycin, dirithromycin, roxithromycin and telithromycin appear unlikely to cause combined hormonal contraceptive failure. Erythromycin is also not considered to cause failure of combined hormonal contraceptives, but isolated anecdotal cases have been reported. An isolated case has also been reported with spiramycin. 

The macrolides such as erythromycin might possibly be expected to suppress the bacteria responsible for the enterohepatic recycling of ethinylestradiol, but good evidence that this is clinically important is scant (see Hormonal contraceptives + Antibacterials Penicillins , p.981). Erythromycin, and to a lesser extent the other macrolides discussed here, also inhibit the cytochrome P450 isoenzyme CYP3A4, which is responsible for the metabolism of the contraceptive steroids. Therefore they might be expected to increase rather than reduce contraceptive efficacy. This would be expected to offset any possible reduced enterohepatic recycling. 

Agents that may increase theophylline levels include allopurinol, beta blockers (nonselective), calcium channel blockers, cimetidine, oral contraceptives, corticosteroids, disulfiram, ephedrine, influenza virus vaccine, interferon, macrolides, mexiletine, quinolones, thiabendazole, thyroid hormones, carbamazepine, isoniazid, and loop diuretics. 

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. 

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