A pharmacist recently told the mother of a patient of mine that taking minocycline reduced the efficacy of her daughter's birth control pill (BCP). The mother called me to discuss this. About once a month I get asked this question. Basically, it is an urban legend. There is no evidence that this is so. Yes, BCPs do occasionally fail, but not because of antibiotics with the exception of Rifampin.
An accessible reference is:
Oral contraceptive efficacy and antibiotic interaction: a myth debunked.
Archer JS, Archer DF. J Am Acad Dermatol. 2002 Jun;46(6):917-23.
Department of Obstetrics and Gynecology, Medical University of South Carolina, Charleston 29425, USA.
Abstract: The purpose of this study was to review the pharmacokinetic and clinical literature regarding the efficacy of oral contraceptives when used concomitantly with antibiotic therapy. Relevant literature was identified by searching MEDLINE and EMBASE. Other sources were located by consulting the bibliographies of the material collected from MEDLINE and EMBASE. Pharmacokinetic evidence demonstrates that plasma levels of oral contraceptive steroids are unchanged with the concomitant administration of antibiotics, including ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline. However, reduced steroid levels have been reported in women taking rifampin with oral contraceptives. Clinical reports of contraceptive failure with antibiotic use are retrospective, have multiple potential biases, and are not supported by pharmacokinetic data. Available scientific and pharmacokinetic data do not support the hypothesis that antibiotics (with the exception of rifampin) lower the contraceptive efficacy of oral contraceptives.
It is time for this urban legend to be recognized for what it is.
