Rifampin and Menstrual Cycle Changes
Yes, rifampin can cause menstrual cycle irregularities by reducing the effectiveness of hormonal contraceptives, which may lead to breakthrough bleeding, spotting, and changes in cycle regularity. 1
Mechanism of Menstrual Changes
Rifampin is a potent inducer of hepatic microsomal enzymes (particularly CYP3A4), which accelerates the metabolism of estrogen and progestin hormones in oral contraceptives. 1
This accelerated hormone metabolism reduces circulating levels of ethinyl estradiol and norethindrone, leading to decreased suppression of the hypothalamic-pituitary-ovarian axis. 2
Studies demonstrate that rifampin significantly decreases both ethinyl estradiol and norethindrone exposure, with increases in follicle-stimulating hormone (FSH) levels by up to 69%, indicating reduced contraceptive suppression. 3, 2
Clinical Evidence of Cycle Disruption
Research shows that rifampin increases ovulation markers and can lead to breakthrough ovulation in some women, even while taking hormonal contraceptives. 4, 5
In one study, 20% of women using etonogestrel implants experienced increased luteal activity after just 2 weeks of rifampin exposure, with one woman presumptively ovulating. 4
The hormonal disruption from rifampin can manifest as irregular bleeding patterns, breakthrough bleeding, or changes in menstrual flow and timing. 2, 5
Duration and Timing Considerations
Full enzyme induction occurs within approximately 1 week of starting rifampin, and the induction effect persists for roughly 2 weeks after discontinuing the medication. 6
Even short courses of rifampin (as brief as 2 weeks) can cause clinically significant decreases in contraceptive hormone levels and changes in ovulation biomarkers. 3, 4
Women should expect potential menstrual irregularities to continue for at least one full menstrual cycle after completing rifampin therapy. 3
Critical Clinical Implications
All women of reproductive potential taking rifampin with hormonal contraceptives should be counseled about the risk of contraceptive failure and advised to add barrier contraception. 1, 3
The interaction affects all hormonal contraceptive methods including pills, patches, rings, and implants—with the notable exception of injectable DMPA (Depo-Provera), which maintains effectiveness with rifampin. 3
Backup contraception should be used during rifampin therapy and continued for at least one full menstrual cycle after stopping treatment. 3