In short, some antibiotics affect hormonal birth control, and some don’t. There are lots of different kinds of antibiotics, and like all prescription drugs, they have to pass rigorous tests and trials. Figuring out how common drugs interact with each other is an important part of ongoing drug safety assessment, so we have good evidence to show which medications work well — or poorly — with each other.
Clinical trials on most common antibiotics have shown that the risk of getting pregnant while taking hormonal contraceptives and antibiotics is no different than the risk of getting pregnant while using the hormonal contraceptive without antibiotics.
A large epidemiological U.S. study involving more than 43,000 women concluded that there is no connection between antibiotic use and a decrease in the effectiveness of hormonal contraceptives. Additionally, a systematic review in 2016 based on 29 studies showed no difference in the occurrence of suppressed ovulation (the main effect of hormonal contraceptives) and breakthrough bleeding while taking non-rifamycin antibiotics and hormonal contraceptives.
Here are some of the types of antibiotics which do not seem to affect hormonal contraceptives:
The only antibiotic that affects hormonal birth control is called rifampicin. It’s a medication used for certain bacterial infections, including tuberculosis and some forms of meningitis.
The main reason why rifampicin is not compatible with hormonal contraceptives is that it affects the way the body metabolizes them. It speeds up the processing of contraceptives in the body and reduces the levels of the main components of birth control (ethinyl estradiol and progestin) in the blood.
A systematic review published in BJOG: An International Journal of Obstetrics & Gynaecology in 2017 shows rifampicin increases the frequency of spontaneous ovulation in women taking hormonal contraceptives.
Rifampicin is the accepted international generic name for the drug across most of the world, but it is also known as rifampin in the U.S. Some manufacturers use specific brand names that can vary from country to country. The generic name should still be clear from the packaging. Rifampicin can sometimes come as part of a combined medication, a tablet that contains a mix of two or more drugs.
Contraceptives that are affected by rifampicin:
- Oral hormonal contraceptives: These include the combined pill and the “minipill” or progestogen-only pill.
- The contraceptive implant: Usually in the upper arm, this small implant releases a gradual supply of hormones to prevent pregnancy.
- The vaginal ring: This is a ring that sits inside the vagina and releases hormones to prevent pregnancy.
- Patches: Hormone-releasing patches that stick to the skin and are changed weekly are normally a good form of contraception, but they are affected by some medications.
Сontraceptives that are not affected by rifampicin:
- The progestogen-only injection: The contraceptive effect is achieved by a progestogen that suppresses ovulation and changes the composition of cervical mucus. Injections are given every eight or 13 weeks.
- IUDs with progestin: This small device is placed in the uterus and secretes the hormone progestogen, which has a contraceptive effect. They’re effective for 3–5 years.
Currently, hormonal contraceptives only work on female sex hormones, so there isn’t a male hormonal contraceptive that can be affected by antibiotics. And antibiotics don’t affect non-hormonal contraceptives like condoms or the copper IUD.
Rifampicin affects the levels of contraceptive hormones present in the body, reducing the effectiveness of hormonal contraceptives.
There are several ways pills can interact with each other, and affecting gut absorption is just one of them. Rifampicin also changes the levels of some of the liver enzymes — chemicals that can affect the way we use hormones — in the body.
If you’re on medication that can change how effective your hormonal contraceptive is, it’s important to take other steps to avoid an unintended pregnancy. This means using a barrier contraceptive like a condom or diaphragm.
Don’t try to “cancel out” the antibiotics by doubling up on birth control pills; the way the medications interact in your body is complicated and unpredictable, so taking a bigger dose of contraceptives doesn’t work.
It isn’t always clear how long antibiotics continue to affect hormonal birth control, so doctors usually recommend continuing to use a barrier method or alternative to hormonal contraception to prevent pregnancy for at least seven days after the end of the antibiotic course. This can be a nice time to try other ways of having sex or being intimate.
Most antibiotics don’t affect hormonal contraception — the one exception is rifampicin (rifampin). If you’re taking rifampicin, it’s essential to use a secondary, non-hormonal method of contraception during the course of antibiotics and for seven days afterward.
Antibiotics aren’t the only medications that can affect birth control, so ask your health care provider when they prescribe any new medications if you’re unsure of their impact on your birth control.