Prilosec Does Not Reduce Oral Contraceptive Efficacy
Omeprazole (Prilosec) does not reduce the efficacy of oral birth control pills. There is no evidence of a clinically significant interaction between proton pump inhibitors like omeprazole and hormonal contraceptives.
Evidence-Based Rationale
No Documented Interaction
The CDC's U.S. Medical Eligibility Criteria for Contraceptive Use does not list proton pump inhibitors, including omeprazole, as medications that interact with oral contraceptives 1.
The only antimicrobial agents documented to reduce oral contraceptive efficacy are rifampin and rifabutin, which are enzyme-inducing antibiotics used primarily for tuberculosis treatment 1.
Broad-spectrum antibiotics, antifungals, and antiparasitics have been studied and show no clinically significant pharmacokinetic interactions with combined oral contraceptives 1.
Mechanism of Known Interactions
The medications that DO reduce oral contraceptive efficacy work through specific mechanisms that omeprazole does not possess:
Enzyme-inducing anticonvulsants (phenytoin, carbamazepine, barbiturates, primidone, topiramate, oxcarbazepine) increase hepatic metabolism of contraceptive steroids through cytochrome P450 induction 1.
Rifampin induces cytochrome P450IIIA subfamily enzymes, which are involved in ethinylestradiol metabolism, leading to decreased contraceptive steroid levels 2.
Omeprazole does not induce these enzyme systems in a manner that affects contraceptive steroid metabolism 2, 3.
Clinical Implications
Women taking omeprazole can rely on standard low-dose oral contraceptives (containing ≥30 mcg ethinylestradiol) for contraceptive protection without requiring backup contraception or alternative methods 1.
No dose adjustment of oral contraceptives is necessary when omeprazole is prescribed 1.
The theoretical concern about gastric pH changes affecting absorption does not translate to clinically significant reductions in contraceptive efficacy, as oral contraceptive steroids are primarily absorbed in the small bowel, not the stomach 4.
Common Pitfall to Avoid
Do not confuse omeprazole with medications that genuinely reduce oral contraceptive efficacy. The documented interacting drugs are limited to specific enzyme-inducing anticonvulsants, rifampin/rifabutin, and certain antiretroviral medications 1. Proton pump inhibitors are not among these agents and should not prompt changes in contraceptive management 1.