How long after antibiotics is birth control effective again

Top things to know

Most antibiotics will not interfere with your hormonal birth control method
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Only rifamycins, including rifampin, will make your birth control less effective
If you are prescribed rifampin, be sure to use back-up protection like condoms or abstain from sex

I’m on hormonal birth control. Can I get pregnant if I take antibiotics?

In most cases, no, as long as you continue to use your hormonal contraception as prescribed you are safe from pregnancy even if you are on antibiotics.

It is a myth that all antibiotics will interfere with the efficacy of your birth control pill.

There is however, one class of antibiotics that is the exception: rifamycins (1).

What do I need to know about Rifamycins?

Rifamycins are a class of antibiotics. The most commonly prescribed rifamycin is known by the name rifampin. (Other types of rifamycins include rifapentine, rifabutin, and rifaximin.) Rifampin is not prescribed very commonly in the United States.

Rifamycins, are most commonly prescribed for the treatment of mycobacterial infections, including tuberculosis (1), or for treating travelers’ diarrhea caused by E. coli (2).

Rifampin can sometimes be used in combination with other antibiotics to treat other bacterial infections too (1). (Fun fact about rifampin: one of the side effects is that it may turn your urine, tears, saliva, and sweat a red color (3).)

Rifampin, can speed up the liver’s ability to break down molecules and medications, including hormonal birth controls, which are processed continually through the liver (3).

For this reason, anyone taking any form of hormonal contraceptive, like the pill, patch, ring, mini-pill, and the implant, who is prescribed rifampin treatment should note that their hormonal contraceptive will not be as effective, and may increase their likelihood of becoming pregnant (3-5).

Rifampin does not interact with other forms of birth control, such as the contraceptive shot, the copper IUD, and the hormonal IUD, meaning that you can continue to use these types of contraception while undergoing rifampin treatment (4,5).

What if my healthcare provider prescribes rifampin for me?

If your healthcare provider does prescribe rifampin to you, be sure to let them know if you are using a hormonal contraceptive.

Unless otherwise stated by your healthcare provider, you can still continue to take your pills as usual every day. However, during this time, it’s important to use non-hormonal birth control methods, like external or internal condoms, or abstain from sex as backup protection during rifampin treatment (3).

If you use birth control pills, consider following the recommendations for what to do if you miss two or more pills:

Continue to use these non-hormonal backup methods for 7 days after you stop taking rifampin, provided you still have 7 hormone-containing pills left in your pack
If there are fewer than 7 hormonal pills left in the pack after you stop taking rifampin, skip the hormone-free pills and start a new pack, but still continue to use back-up contraception for the first 7 pills of the pack (6).

If you are using another form of hormonal contraceptive, like the patch or ring, speak to your healthcare provider.

Things to keep in mind, when you’re sick

Even if you aren’t on rifampin, being ill is hard on the body and mind. If you are sick, it’s easy to lose track of time and responsibilities, and you might forget to take your pill (or other daily medication). Use Clue to set up pill reminders, or task a family member, partner, or friend, to help remind to make sure to take your contraceptive pill daily at the same time.

Use the Clue app to set up daily pill reminders.

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screens of the Clue app

OB/Gyn > General OB/GYN

— Researchers urge extra precautions to avoid unintended pregnancy

by Amanda D'Ambrosio, Staff Writer, MedPage Today August 18, 2020

The combined use of broad-spectrum antibiotics and hormonal birth control was associated with a higher risk of unintended pregnancy, researchers found.

Individuals who used antibiotics while taking hormonal contraceptives -- such as the pill, patch, or ring -- were nearly seven times as likely to get pregnant (odds ratio 6.7, 95% CI 2.9-16.0), according to Jeffrey Aronson, DPhil, of Oxford University, and Robin Ferner, MD, of the University of Birmingham, both in England.

Enzyme-inducing medications, which have known effects on the efficacy of hormonal birth control, were associated with 13 times the risk of unintended pregnancy (OR 13.0, 95% CI 5.5-31.0), the team reported online in BMJ Evidence-Based Medicine.

The researchers suggested that unintended pregnancy may occur by a few different mechanisms, including the effects of antibiotics on increasing hepatic metabolism of hormones, altering gastrointestinal function, and changing physiochemical factors in the gut that may affect the absorption of synthetic estrogen and progesterone.

Ferner told MedPage Today that the findings should encourage physicians to tell their patients that "it's safest to take extra precautions to avoid unintended pregnancy."

"We don't know from our data how many unplanned pregnancies occur as a result of broad-spectrum antibiotics," he said in an email. "But for some women, even a 1:1,000 chance of an unintended pregnancy would be too much."

The researchers recommended that individuals who do not wish to get pregnant either stop having sex, or use a condom in addition to hormonal birth control while taking antibiotics and for 7 days after completing the course.

Asked for her perspective, Carrie Cwiak, MD, MPH, director of the family planning division at Emory University School of Medicine in Atlanta, said that while the research suggests an association between unintended pregnancy and antibiotic use, "it doesn't seem to fit with some of the studies early on."

Cwiak added that some mechanisms of unintended pregnancy suggested by the investigators need further clarification, such as the possibility that antibiotic use might affect levels of ethinylestradiol -- i.e., synthetic estrogen -- in certain patients.

"Ethinylestradiol is in fact not the main driver of contraceptive effect in hormonal contraceptives," Cwiak told MedPage Today. "It is the level of synthetic progesterone in the medication that you're using that provides the majority of contraceptive effect."

She noted that although the CDC does not recommend precautions for the combined use of hormonal birth control methods and broad-spectrum antibiotics, the study indicates an opportunity to further explore the interaction of these two medications.

For the study, Aronson and Ferner conducted a database review of Yellow Card reports to the U.K.'s Medicines and Healthcare products Regulatory Agency, including all reports that mentioned unintended pregnancy.

The researchers looked at three different kinds of medications: non-enzyme-inducing antibiotics, enzyme-inducers, and commonly used control medicines, including ibuprofen and citalopram. Non-enzyme-inducing medications included amoxicillin, ampicillin, cephalexin, ciprofloxacin, erythromycin, metronidazole, nitrofurantoin, oxytetracycline, and trimethoprim.

The primary outcome of the study was unintended pregnancy. The researchers also assessed for congenital abnormalities, cardiac arrhythmias, and headaches, and looked at diarrhea as a potential confounding factor.

In the analysis of 173,073 spontaneous reports, the investigators found that patients who took enzyme-inducing medications had the highest rate of unintended pregnancy (119 per 100,000, 95% CI 81-156). The rate of unintended pregnancy was 62 per 100,000 among those who took antibiotics (95% CI 44-79), and 6 per 100,000 among those in the control group (95% CI 2-16).

The risk of congenital abnormalities was higher among individuals who took enzyme-inducing medications, but not among the cohort who took broad-spectrum antibiotics. Diarrhea was not a confounding factor.

Aronson and Ferner acknowledged that the research is limited based on the use of adverse reports, so the actual number of unintended pregnancies and combined users of hormonal contraceptives and antibiotics is thus unknown. In addition, it was not possible to calculate absolute risk.

Cwiak stated that although further research is needed about the drug interactions of antibiotics and hormonal birth control, it is important to emphasize the need to counsel patients to keep using their chosen contraceptive method. When taking the medications in question, dual protection is the safest choice, she noted.

"We hear too many negative messages about birth control overall, and the benefits by far outweigh the risks," Cwiak said. "At the end of the day, our message has to be birth control positive."

Amanda D'Ambrosio is a reporter on MedPage Today’s enterprise & investigative team. She covers obstetrics-gynecology and other clinical news, and writes features about the U.S. healthcare system.

Disclosures

Aronson and Ferner reported that "they have both written widely about adverse drug reactions and interactions and have from time to time received fees for legal reports, payments for articles, and royalties on books that they have written on the subject."

How long does it take for birth control to work after antibiotics?

You may be asked to take this contraception in a different way from usual and use condoms as well. You'll need to continue this for 28 days after finishing the antibiotics.

How long does antibiotics affect the pill?

Research shows that, in fact, most antibiotics have no effect on how the pill works. So, if a woman is on an antibiotic for a common infection such as sore throat, chest infection or UTI, there is generally no need to worry about doubling up with extra protection. The pill will continue to work perfectly well.

What are the chances of getting pregnant on antibiotics and birth control?

While some women have gotten pregnant while taking antibiotics and hormonal birth control at the same time, these reports are rare. Your chances of getting pregnant while taking most types of antibiotics are no higher than the normal failure rate of birth control, which is 6 to 9%.

How long does it take for birth control to start working again?

That means that if your period starts on a Wednesday morning, you can start the pill up to the following Monday morning to be protected right away. If you start at any other time during your menstrual cycle, you'll be protected from pregnancy after 7 days of using the pill.