If you’ve ever taken birth control pills and antibiotics at the same time, you may have been told that antibiotics make the pills less effective. Many antibiotic information sheets come with a warning that say antibiotics may make birth control pills less effective. Does evidence support the claim, or is it just a myth?
Birth control pills are a form of hormonal contraception meant to prevent pregnancy. Most birth control pills contain the two hormones estrogen and progesterone. This helps block the release of eggs from the ovary, or ovulation. Some birth control pills, such as the minipill, help thicken cervical mucus to make it more difficult for sperm to reach an unfertilized egg.
To date, the only antibiotic proven to impact birth control pills is rifampin. This drug is used to treat tuberculosis and other bacterial infections. If you take this medication while using birth control pills, it decreases the hormone levels in your birth control pills. This decrease in hormone levels can affect whether ovulation is prevented. In other words, your birth control becomes less effective. Rifampin also decreases hormone levels in the birth control patch and vaginal ring.
Other drugs may make birth control less effective, such as:
- some anti-HIV protease inhibitors
- some anti-seizure medications
- the antifungal drug griseofulvin
Birth control pills may make other drugs less effective, such as analgesics and blood pressure medications. The effects of antidepressants, bronchodilators, and tranquilizers may be increased when you use them with birth control pills.
There isn’t much scientific research on the adverse side effects of taking antibiotics with birth control pills. In theory, similar side effects of both drugs may worsen when both types of drugs are taken together. These side effects may include:
- changes in appetite
Side effects vary depending on the person and the class of antibiotic taken. Not everyone who takes birth control pills and antibiotics experiences negative side effects.
Despite anecdotal evidence that antibiotics lessen the effectiveness of birth control pills, there may be other factors at play that lead to birth control failure. For example, you may not take your birth control pills on time or you may skip a pill or two if you’re ill. You may not absorb the pill properly if you’re vomiting. While it may seem that antibiotics are to blame, it may be a coincidence.
When used as directed, birth control pills are up to 99 percent effective in preventing pregnancy. Most birth control pills are taken daily for 21 days on and seven days off. Some pills are taken for 28 straight days and others for 91 straight days. Pills may be different colors to indicate different levels of hormones. Some days you may take pills that contain no hormones. They’re meant to keep you in the habit of taking your pills.
Your doctor will advise you about when to start taking your pills. This is usually the first Sunday after your menstrual cycle starts or the first day of your menstrual cycle. You should take your pills at the same time each day. If you don’t take your pills consistently, your risk of becoming pregnant increases.
Birth control pills are just one of many birth control options. Other options include:
The U.S. Department of Health and Human Services recommends asking yourself these questions when deciding which option is best for you:
- Do you want to have children some day?
- Do you have any medical problems?
- How often do you have sex?
- How many sex partners do you have?
- Will the birth control prevent HIV and other sexually transmitted diseases?
- How well does the birth control work?
- What are the side effects?
- Is it difficult or inconvenient to use?
When it comes to birth control pills, the options can be confusing. Not every woman is a good candidate for every type of birth control pill. For example, if you’re older than 35 and you smoke or have a history of heart disease or stroke, then combination birth control pills may not be a good choice for you. If you have breast cancer or unexplained uterine bleeding, minipills may not be the best fit.
The best person to help you figure out the best birth control for you is your doctor. They can discuss the pros and cons of each method with consideration for your specific situation and answer your questions.
With the exception of the drug rifampin, there’s little evidence that antibiotics interfere with birth control pills. More research is needed, and some doctors believe there’s not enough evidence to disprove the risk. To be on the safe side, you may want to use a backup form of birth control, such as a condom or diaphragm, while taking antibiotics.