Title: Effect of antibiotics and oral contraceptive efficacy.

POPLINE Document Number: 077621

Author(s):

Zachariasen RD

Source citation:

JOURNAL OF DENTAL HYGIENE, 1991 Sep;65(7):334-8.

Abstract:

It is estimated that 10 million American women are currently taking oral contraceptives (OCs) on a daily basis. Outpatient prescription drug use from 1971 to 1981 amounted to 55 million prescriptions for OCs annually in US. In recent years, reports have linked the loss of contraceptive efficacy with the concurrent administration of other drugs. Experimental data suggest that the antitubercular drug, rifampicin, reduces the efficacy of OCs by stimulating their hepatic degradation. In the presence of antibiotics OCs may fail because of reduced intestinal absorption of contraceptive steroids resulting from alterations in the intestinal bacterial flora. A study of 5 women taking OCs and tetracycline or ampicillin demonstrated increased excretion of OCs and decreased half-life. In one study, it was found that over 70% of physicians' and hospital records were incorrect regarding medications that the patients were taking. The rates of pregnancy for OCs vary from less than 1 pregnancy/100 woman-years for high-dose estrogen (35 mg or more of ethinyl estradiol) to slightly more than 1 pregnancy/100 woman-years for low-dose preparations (under 35 mg of ethinyl estradiol). A total of 63 pregnancies resulting from antibiotic-oral contraceptive interactions were reported between 1968 and 1984 in England. Penicillin and tetracyclines were the 2 antibiotics most often cited as being associated with these pregnancies; 32 for penicillin and 12 for the tetracyclines. Through 1985, there had been only 150 published reports of pregnancies from all drug interactions with OCs, thus the risk of pregnancy resulting from antibiotic/OC interaction is small. In view of the potential of drug interactions that affect OC efficacy and the common practice of prescribing antibiotics, dental professionals should be aware of possible OC failure with these drugs.

Keywords:

United States
England
Oral Contraceptives
Antibiotics
Drug Interactions
Contraception Failure
Developed Countries
North America
Americas
United Kingdom
Europe, Western
Europe
Contraceptive Methods
Contraception
Family Planning
Drugs
Treatment
Contraceptive Usage