Oral Contraceptive Drug Interactions

A review of diagnosis and treatment of acne in adult female patients

“…Of note, there is limited evidence on the administration of antibiotic agents and the potential impact on the effectiveness of oral contraceptive pills ( Hoffmann et al, 2015 ). Although a large epidemiological study that was conducted in the United States showed that there is no association between concomitant antibiotic use and the risk of breakthrough pregnancy among oral contraceptive pill users ( Guengerich, 1990 ), other studies have shown a potential relationship ( Back et al, 1980 , Bainton, 1986 , Fazio, 1991 , Skolnick et al, 1976 ). There are three categories of antibiotic agents that range from those that are likely to reduce the effectiveness of OCPs (rifampin), those that are associated with OCP failure in three or more reported cases (ampicillin, amoxicillin, metronidazole, and tetracycline), and those that were associated with OCP failure in at least one case report (cephalexin, clindamycin, dapsone, erythromycin, griseofulvin, isoniazid, phenoxymethylpenicillin, talampicillin, and trimethoprim; Miller et al, 1994 ).…”

Antibiotic and Oral Contraceptive Drug Interactions: Is There a Need for Concern?

“…Antibiotics can interrupt the enterohepatic cycling of estrogens by reducing the bacterial population of the small intestine, which is responsible for hydrolysis of the glucuronide moiety (estrogen metabolite found in bile) to free drug (6). When the gut flora are altered, enterohepatic circulation is reduced, the metabolite is excreted, resulting in lower circulating concentrations of ethinylestradiol.…”

“…Nevertheless, individual case reports and small, retrospective studies have led to the inclusion of warnings in the Compendium of Pharmaceuticals and Specialties (13) and other references about possible interactions between oral contraceptives and other antibiotics. Prospective studies are lacking or inconclusive for these antibiotics (2,4,6,10). With a recognized failure rate of 1% or less/year in women taking oral contraceptives as directed and 3%/year in typical populations, thousands of pregnancies occur each year in the millions of women taking oral contraceptives.…”

“…Antibiotic/oral contraceptive interactions Adapted from references 2,4,[6][7][8][9][10][11]13,[16][17][18][19][20][21][22][23] A correlation exists between griseofulvin and oral contraceptive failure because four women experienced recurrence of original symptoms (intermenstrual bleeding, amenorrhea) upon re-exposure to the antifungal agent (17) ( Table 1). It appears that with terbinafine (Lamisil, Novartis Pharmaceuticals Canada Inc, Dorval, Quebec), a newer oral antifungal agent, the significance of this interaction is lessened (4).…”

Effects of Rifabutin and Rifampicin on the Pharmacokinetics of Ethinylestradiol and Norethindrone

“…Antibiotics, such as penicillins and tetracyclines, have been shown to impair hydrolysis of estrogen conjugated by inhibiting bacterial gut flora and, as such, decrease the amount of estrogen recovered in the urine. 4,6,7 Rifampicin is a broad-spectrum antibiotic used for treatment of tuberculosis, for synergy against grampositive infections, and to eradicate resistant bacteria in chronic carriers. Rifampicin is also a potent inducer of CYP3A4 in vitro and in vivo, and concomitant administration with oral contraceptives has been shown to reduce systemic exposure to and half-lives of both ethinylestradiol and norethindrone.…”