Categories: Drugs/Metabolism

What Antibiotics interfere with OCP?

  1. Rifampin is the antibiotic that is classically stated to be avoided in women taking OCPs

HOW? Rifampin is a potent inducer of cytochrome P450 3A4 and accelerates the elimination of ethinyl estradiol and some progestin components, resulting in an increased risk of OCP failure

OTHER DRUGS TO AVOID: Griseofulvin (an antifungal), Phenytoin, St. John’s Wort and Chronic Alcohol use (can all induce CYP 3A4)


1. Barditch-Crovo P, Trapnell CB, Ette E et al (1999) The effects of rifampin and rifabutin on the pharmacokinetics and pharmacodynamics of a combination oral contraceptive. Clin Pharmacol Ther 65:428–438

2. Pelkonen, Olavi et al. Inhibition and induction of human cytochrome P450 enzymes: current status. Arch. Toxicol. October 2008, Volume 82, Issue 10, pp 667-715

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Dr. C Humphreys

Internal Medicine

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