Yes. Some medicines and herbal supplements can make certain hormonal birth control methods less effective, which may raise the chance of pregnancy. The best-known examples include rifampin or rifabutin, some anti-seizure medicines, certain HIV medicines, and St. John’s wort. Most ordinary antibiotics do not interfere. The risk depends on the medicine and contraceptive method, so check with a pharmacist or prescriber before starting or stopping anything.
Birth control is designed to prevent pregnancy when used correctly, but certain medicines can interfere with how well some contraceptive methods work. These interactions do not affect every method in the same way, and many commonly prescribed medicines can be used alongside contraception without reducing its effectiveness. Knowing which medicines need extra attention can help you choose the right precautions and avoid unnecessary changes to your treatment.
Which medicines can make birth control less effective?
Some medicines can reduce the effectiveness of hormonal contraception, including certain pills, patches, vaginal rings, implants, and progestin-only pills. The risk depends on the specific drug, its effect on contraceptive hormones, and the method being used. The Centers for Disease Control and Prevention (CDC) identifies several important interactions involving combined hormonal contraceptives.
- Rifampin and rifabutin: These antibiotics can reduce the effectiveness of certain hormonal contraceptives. They are important exceptions to the general rule that most antibiotics do not interfere with birth control.
- Certain anti-seizure medicines: Carbamazepine, phenytoin, topiramate, oxcarbazepine, primidone, and some barbiturates can reduce the effectiveness of certain hormonal methods.
- Some HIV medicines: Particular antiretroviral medicines can interact with hormonal contraceptives. The effect varies depending on the drug combination and contraceptive method.
- St. John's wort: This herbal supplement, sometimes taken for mood-related concerns, may reduce the effectiveness of hormonal contraception.
- Other interacting medicines: Certain additional drugs can affect hormonal contraceptives or emergency contraceptive pills. A pharmacist or prescriber can check the specific medicine and method involved.
These medicines do not all carry the same risk, and they do not necessarily affect every contraceptive method. The CDC guidance on progestin-only contraception explains that some anti-seizure medicines and rifampin or rifabutin can reduce the effectiveness of progestin-only pills and contraceptive implants. The recommended precautions therefore depend on the exact combination.
Do antibiotics affect birth control pills?
Most antibiotics used to treat common infections do not make hormonal birth control less effective. Taking an ordinary antibiotic does not automatically mean you need to stop your contraceptive pill or use a second method. Rifampin and rifabutin are important exceptions because they can interfere with some hormonal contraceptives.
The National Health Service (NHS) explains that rifampicin and rifabutin can reduce the effectiveness of the combined contraceptive pill and that additional contraception may be needed. If either medicine has been prescribed, ask your prescriber or pharmacist which contraceptive precautions are appropriate. Do not stop a prescribed antibiotic or change your birth control routine without obtaining advice.
Does the type of birth control matter?
Yes. Drug interactions are method-specific, so a medicine that affects one contraceptive method may not affect another in the same way. Knowing whether you use a pill, patch, vaginal ring, implant, injection, or intrauterine device (IUD) helps a healthcare professional determine whether an interaction is relevant.
Birth control pills, patches, and vaginal rings
Combined pills, patches, and vaginal rings contain hormones that prevent pregnancy. Certain enzyme-inducing medicines, including rifampin and some anti-seizure drugs, can reduce the effectiveness of these methods. Some progestin-only pills can also be affected by particular interacting medicines. Your clinician may recommend a different contraceptive method or a temporary backup method, depending on the medicine and how long you need to take it.
Contraceptive implants
Hormonal implants release a progestin to prevent pregnancy. Some enzyme-inducing medicines can lower the effectiveness of these implants. This matters particularly when a medicine is needed for an extended period, because relying on an affected implant alone may not provide the expected protection. Discuss other contraceptive options with your healthcare professional before making any changes.
Contraceptive injections and IUDs
Some contraceptive options are less affected by the medicines discussed above. The CDC states that the depot medroxyprogesterone acetate injection is not expected to lose effectiveness with rifampin, rifabutin, or certain anti-seizure medicines. IUDs also avoid many of the interactions that affect hormonal methods processed through the body. However, the appropriate choice depends on your medical circumstances, other medicines, and personal preferences.
The CDC's guidance on intrauterine devices provides information about how particular medicines relate to copper and hormonal IUD use. A healthcare professional can help determine whether an IUD or another method would be suitable if you need long-term treatment with an interacting drug.
Can medicines affect emergency contraception?
Yes. Certain enzyme-inducing medicines, including rifampin and some anti-seizure medicines, may reduce the effectiveness of emergency contraceptive pills. St. John's wort and certain other medicines can also be relevant. This means that choosing emergency contraception may require more care if you take an interacting medicine.
If you have had sex without effective contraceptive protection and are concerned about a drug interaction, contact a pharmacist, sexual health service, or healthcare professional as soon as possible. Explain which birth control method you use and the names of all your medicines and supplements. A copper IUD may be an option for emergency contraception, and a professional can advise which approach is appropriate. The CDC's emergency contraception guidance discusses medicines that may interfere with emergency contraceptive pills.
Can vomiting or diarrhea affect birth control pills?
Yes. Even when a medicine does not directly interact with contraceptive hormones, an illness or medication side effect can affect an oral contraceptive if it causes vomiting or significant diarrhea. Depending on the pill and the timing of the symptoms, the medicine may not be absorbed as expected.
What to do depends on the type of pill, when vomiting occurred, and how long diarrhea lasted. The NHS guidance on sickness or diarrhea while taking the combined pill explains when a replacement pill or additional contraception may be needed. Progestin-only pills have their own instructions, so check the leaflet supplied with your medicine or ask a pharmacist rather than applying combined-pill instructions to every contraceptive.
What should you do if a new medicine may interfere with birth control?
You do not need to avoid necessary treatment simply because you use contraception. The goal is to identify potential interactions and select precautions that maintain pregnancy prevention while allowing you to receive appropriate care.
- Tell your prescriber about your contraceptive method. Include the exact name of your pill, patch, ring, implant, injection, or IUD if known.
- Provide a complete medication list. Include prescription medicines, over-the-counter products, herbal supplements, and medicines you take only occasionally.
- Ask whether backup contraception is needed. If an interaction is possible, the advice may involve condoms, a different contraceptive method, or another precaution for a specified period.
- Discuss long-term treatment before changing methods. If you need an interacting medicine for months or longer, a contraceptive method less affected by that medicine may be worth considering.
- Seek prompt advice after possible contraceptive failure. If you have had sex and suspect your protection was reduced, ask about emergency contraception without delaying unnecessarily.
Do not stop an essential medicine, double your contraceptive dose, or change methods without appropriate advice. Some interactions also work in the opposite direction: hormonal contraception can alter the effects of certain other medicines. Your healthcare professional should consider both sides of the interaction when reviewing your treatment.
How can you check whether your medicines are compatible?
Start by checking the patient information leaflet for your contraceptive and any newly prescribed medicine. However, a leaflet may not provide enough information to determine how an interaction applies to your specific combination. A pharmacist or prescriber can use current drug-interaction references to assess the risk and explain whether you need backup protection or a different contraceptive option.
Make this check whenever you start or stop a prescription medicine, begin an herbal supplement, or change the dose of a medicine that may interact with contraception. Also ask how long any precautions should continue after the interacting medicine is stopped, because that interval can differ between drugs and contraceptive methods.