Should women of childbearing age who require antibiotics be advised that such medications may decrease the effectiveness of oral contraceptives (OCs) and therefore, they should abstain or use a backup method? Also, am I correct to assume that a negative beta human chorionic gonadotropin (β-hCG) test is advised prior to starting isotretinoin (which is teratogenic)?
—Dean Sparks, PA-C, Exeter, Calif.

The possibility that common antibiotics might reduce OC effectiveness has been recognized for years; the AMA recommends that women be informed of this risk and advised to use nonhormonal backup methods. Antibiotics of potential concern include rifampin, the penicillins, the cephalosporins, and tetracycline. The mechanism of action is interference of these drugs with the pharmacokinetics of ethinyl estradiol. Because of its proven teratogenicity, isotretinoin should never be prescribed to a woman who has not had a negative pregnancy test.

Prescribers and patients who plan to use the drug must now register with iPLEDGE (; phone: 866.496.0654), a risk-management program designed to eliminate fetal exposures to isotretinoin. See Martin KA, Barbieri RL. Overview of the use of estrogen-progestin contraceptives. In: Rose BD, ed. UpToDate. Wellesley, Mass.: UpToDate; 2008.
—Reuben W. Zimmerman, PA-C (117-17)

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