Risk for ovulation in women taking a low-dose oral contraceptive (Microgynon) when receiving antibacterial treatment with a fluoroquinolone (ofloxacin)

Abstract

The possibility of escape ovulation in women using a fluoroquinolone ofloxacin for antibacterial treatment at a dose of 200 mg twice daily for 7 days when taking a combined oral contraceptive (Microgynon, 150 micrograms levonorgestrel and 30 micrograms ethinyl estradiol) was studied in 20 women. By using a placebo-controlled, randomized, cross-over design 6 contraceptive pill cycles were followed. Follicle-stimulating hormone and estradiol concentrations were measured on tablet days 5-8, 19-21; progesterone was assayed on days 19-21 during treatment with ofloxacin or placebo. Ultrasonographical investigations for measurements of the number and diameter of ovarian follicles were performed on one of days 5-10, 11-17, 18-24, 25-28. No indications of ovulation during ofloxacin medication were detected. It is concluded that alternative contraceptive precautions should not be needed when ofloxacin is prescribed for patients taking oral contraceptives.

Drug interactions between non-rifamycin antibiotics and hormonal contraception: a systematic review

“…25 Two additional trials reported no ovulation by serum progesterone and/or monitoring of follicles on ultrasound scanning in OC cycles with and without temafloxacin or ofloxacin. 26,27 Pharmacokinetic outcomes. Two studies reported no change to HC pharmacokinetic with fluoroquinolones.…”

FFPRHC Guidance (April 2005) Drug interactions with hormonal contraception

“…A small, randomised, doubleblind, crossover study investigated the effect of ofloxacin 200 mg twice daily on ovulation in women using a 30 µg EE COC. 99 No evidence of ovulation, by ultrasound scan and serum progesterone, was found.…”

Contraceptive Choices for Women with Inflammatory Bowel Disease

“…22 Two small, prospective, randomised-controlled trials investigated the effects of antibiotics (ciprofloxacin and ofloxacin) on markers of ovulation in women using COCs and found no evidence of ovulation. 24,25 Despite lack of evidence of the effects of antibiotics on gut flora, additional contraception is advised when starting a new broad-spectrum, nonenzyme-inducing antibiotic and for 7 days after discontinuation in keeping with previous Faculty Guidance. 26 Women who are established on a nonenzyme-inducing antibiotic long-term do not require additional contraception unless they change to a different antibiotic.…”