Do Nonhepatic-Enzyme–Inducing Antibiotics Cause Oral Contraceptives to Fail?

Although pharmacokinetic and other data suggest that common nonhepatic-enzyme–inducing antibiotics do not impair the efficacy of oral contraceptives (OCs), the studies have been small. In an analysis of data published by Britain's healthcare regulatory authority between 1963 and 2018, investigators assessed spontaneous reports of suspected adverse drug reactions (ADRs) — including unintended pregnancy — while taking medications in the following categories:

• Nine nonhepatic-enzyme–inducing antibiotics (e.g., ampicillin, cephalosporins, tetracyclines; >74,000 reports)

• Twelve hepatic-enzyme–inducing medications (e.g., carbamazepine, nevirapine, rifampicin; >32,000 reports)

• Nine ‘control' medications commonly used by reproductive-aged women and not…