Ask the Experts: Answers to questions on IUS use, OC interactions

Can women who are breast-feeding use a levonorgestrel intrauterine system? What is the impact of fluconazole (Diflucan, Pfizer; New York City), an oral medication used to treat vaginal yeast infections, on oral contraceptive (OC) efficacy?

Comments are offered by David Archer, MD, professor of obstetrics and gynecology and director of the Clinical Research Center at the Eastern Virginia Medical Center in Norfolk; Linda Dominguez, RNC, NP, assistant medical director of the Albuquerque-based Planned Parenthood of New Mexico; Andrew Kaunitz, MD, professor and assistant chair in the obstetrics and gynecology department at the University of Florida Health Science Center/Jacksonville; 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 work as a nurse practitioner in a small health department, and we see patients wanting the Mirena (levonorgestrel intrauterine system [LNG-IUS], Berlex Laboratories, Montville, NJ). It is listed in the package insert to avoid breast-feeding mothers due to the levonorgestrel component. I think it would be a good method at six weeks out for a postpartum mother whether she is breast-feeding or not. I need backup. Can you help?

Wysocki: The Geneva-based World Health Organization (WHO) lists use of the LNG IUS [at] six weeks postpartum, the same as for progestin-only OCs.1

Question: What impact does fluconazole have on OC efficacy?

Archer: There are two papers on the pharmacokinetics of ethinyl estradiol with the administration of a single and multiple doses of fluconazole.2,3 Both papers indicate an increase in the serum levels of ethinyl estradiol after administration of fluconazole.

One article also investigated the effect of fluconazole on norethindrone and found a similar increase in serum levels after fluconazole administration.2 These two articles would indicate that there is no loss of efficacy of the contraceptive steroids with the concomitant administration of fluconazole, even at high doses.

Dominguez: In regard to OC failure issues, clinicians recognize that any negative health or psychosocial change can be an impediment to correct contraceptive use.

If a sexually active woman is preoccupied and suffering the unpleasant symptoms of genital itching and discharge, she may well be less alert to utilizing her contraceptive pill, patch, ring, or barrier method and less inclined to have sexual relations.

It is recognized that vulvovaginal candidiasis is likely to flare around menses/withdrawal bleed time because of the increase in the glycogen-rich vaginal environment. If a woman is dealing with vaginal symptoms, she may be distracted from starting a new pack or ring/patch cycle and have a prolonged hormone-free interval.

Kaunitz: Two well-designed pharmacokinetic trials have found that estrogen and progestin levels are NOT lowered in OC users administered fluconazole.2,3 Of note, steroid levels are increased with use of the oral antifungal agent. Therefore, use of fluconazole will not increase risk of contraceptive failure, but it might increase risk of side effects in OC users.

Wysocki: WHO does not list fluconazole in its list of OC/drug interactions, and it makes a special point about long-term use of the drugs they do list.1 Fluconazole is generally taken in one dose for the treatment of vaginal candidiasis.


1. World Health Organization, Department of Reproductive Health and Research. Medical Eligibility Criteria for Contraceptive Use. 2nd ed.; 2000. Accessed at

2. Hilbert J, Messig M, Kuye O, et al. Evaluation of interaction between fluconazole and an oral contraceptive in healthy women. Obstet Gynecol 2001; 98:218-223.

3. Sinofsky FE, Pasquale SA. The effect of fluconazole on circulating ethinyl estradiol levels in women taking oral contraceptives. Am J Obstet Gynecol 1998; 178:300-304.