Ask the Experts: Answers to questions on OC use, DMPA impact

[Editor’s note: What’s the impact of concomitant medications on combined oral contraceptives (OCs)? Commenting this month are Andrew Kaunitz, MD, professor and assistant chair in the obstetrics and gynecology department at the University of Florida Health Science Center/Jacksonville; Anita Nelson, MD, professor in the obstetrics and gynecology department at the University of California in Los Angeles (UCLA) and medical director of the women’s health care clinic and nurse practitioner training program at Harbor-UCLA Medical Center in Torrance; Sharon Schnare, RN, FNP, CNM, MSN, women’s health consultant and clinician with the Seattle King County Health Department in women’s and adolescent health care and the International District Community Health Center in Seattle; Felicia Stewart, MD, adjunct professor in the department of obstetrics, gynecology, and reproductive sciences at the University of California-San Francisco and co-director of the Center for Reproductive Health Research & Policy; and Susan Wysocki, RNC, NP, president and chief executive officer of the Washington, DC-based National Association of Nurse Practitioners in Women’s Health.]

Question: I have several patients who are on short or long-term antibiotics, are on the Pill, and use backup condoms. My question: Should a woman on oral contraceptives (who hasn’t missed any pills and taken them consistently) and antibiotics use emergency contraception (EC) if her condom fails?

Kaunitz: Contrary to what many of us have been taught, standard courses of single antibiotics, including doxycycline, ampicillin, quinolones, and metronidazole, have not been found to lower estrogen/progestin levels in women using combination OCs.1 Keep in mind, however, that the studies that generated the above reassuring findings were performed in women taking one (not two) antibiotics. In contrast with other antibiotics, use of rifampin (sometimes used to treat tuberculosis or other infections) without question lowers steroid levels in OC users; when this hepatic enzyme-inducing antibiotic is prescribed, women using OCs (or patches, rings, or the combination injectable) should use barrier backup contraception. (Editor’s note: Kaunitz served as a consultant in the development of the Washington, DC-based American College of Obstetricians and Gyne-cologists practice bulletin, The Use of Hormonal Contraception in Women with Coexisting Medical Conditions, referenced above.)

Nelson: Since she does not need to use the condom for birth control in the first place, she does not need to use EC if the condom breaks. I assume she is using it for protection against sexually transmitted diseases, since every study has shown us that the antibiotics that are typically used for long-term treatment of acne do not reduce the serum levels of hormones to the subtherapeutic range.2

Schnare: No, she need not use backup condoms when taking OCs and using antibiotics. The only medications associated with OC failure include rifampin, griseofulvin, and anticonvulsants (except valproic acid).

Stewart: This is certainly being "extra" careful! The only antibiotics that have been shown to reduce pill efficacy are the anti-tuberculosis drugs such as rifampin. There is no real research evidence that use of common short or long-term medications such as doxycycline, urinary tract infection treatment, or penicillin have any effect. That said, there is no harm in using condoms as a back up, and EC for condom failure as well. The general rule I use is to provide EC whenever the woman wants to use it — even if we think the chance of pregnancy is really low. It’s her call.

Wysocki: This is a pretty typical question, for which there is NO evidence to support that common antibiotics — tetracycline, in particular — cause Pill failure. Please see the guidelines issued by the World Health Organization (WHO). Griseofulvin and rifampin are the only antibiotics that may affect the Pill per WHO guidelines. [To access the guidelines, "Improving Access to Quality Care in Family Planning. Medical Eligibility Criteria for Contraceptive Use," on-line, go to the WHO web site (, click on "WHO Sites," "Reproduc-tive Health & Research," "Family Planning," and "Family Planning Materials." Click on the publication title, which will allow you to browse the publication by chapter.]


1. Clinical Management Guidelines for Obstetrician-Gynecologists. The use of hormonal contraception in women with coexisting medical conditions. Washington, DC: American College of Obstetricians and Gynecologists; 2000. ACOG Practice Bulletin; 18.

2. Zieman M, Nelson A. Combination OCs and prescribed antibiotics. The Female Patient 2002; 27:40-41.