The following prescription drugs and dietary supplements commonly affect how well birth control works:
- Some anti-seizure medications
- Some antibiotics
- HIV medications
- St. John’s Wort
Before we talk about how your meds can interfere with your birth control, let’s take a moment to understand how birth control works.
How does hormonal birth control work?
Some birth control methods (“barrier contraception”) are not hormonal—for example, diaphragms, cervical caps, and male and female condoms. We’re not talking about those here.
Most women use hormonal forms of birth control—meaning, birth control that releases hormones into the body to prevent a pregnancy. Most pills contain a mix of the hormones, progestin and estrogen, as do the patch (Xulane) and the vaginal ring (e.g., NuvaRing). Some pills (like “minipills”) and other birth control methods such as injections, implants (Nexplanon), and intrauterine devices (IUDs), release only progestin into the woman’s body.
Progestin, the common active ingredient in all types of hormonal birth control, prevents pregnancy in a few different ways:
- It makes it difficult for sperm to pass through the cervix and fertilize the egg.
- It makes ovulation less likely.
- It thins the lining of the womb making it less likely that a fertilized egg can stick.
Estrogen is combined with progestin in most contraceptive pills, the patch, and the vaginal ring. It prevents pregnancy by preventing ovulation.
So far, so good.
Unfortunately, some medications make hormonal contraception less effective. Let’s look at what those are here.
Which medications stop birth control from working?
Some medications interfere with your birth control, especially if (like most women), you use the pill, the patch, or the vaginal ring. Here is a rundown of the possible interactions, as well as some suggestions for safer alternatives.
Anti-seizure medications or “anticonvulsants”
- Anticonvulsants that interact with birth control: Barbiturates, primidone, phenytoin, Tegretol, Trileptal (used to treat nerve pain), and topiramate (used to treat migraines).
- Anticonvulsants that don’t interact with birth control: Gabapentin, levetiracetam, and tiagabine.
- Safest contraception options: In most cases, the birth control shot (Depo-Provera), hormonal implant (Nexplanon), hormonal IUD (e.g., Mirena, Kyleena), and copper IUD are all safe to use with anticonvulsants. Non-hormonal methods are another safe alternative.
- Good to know: Hormonal contraception makes lamotrigine less effective at preventing seizures, so these shouldn’t be taken together.
Some antibiotics
- Antibiotics that interact with birth control: Antibiotics used to treat tuberculosis (rifampin and rifabutin).
- Antibiotics that don’t interact with birth control: All other antibiotics! No other antibiotics have been proven to affect hormonal birth control methods.
- Safest contraception options: In most cases, the birth control shot (Depo-Provera), hormonal implant (Nexplanon), hormonal IUD (eg. Mirena, Kyleena), and copper IUD are all safe to use with antibiotics for TB. Non-hormonal methods are another safe alternative.
- Good to know: Some anti-fungals (griseofulvin, miconazole) were thought to cause birth control failure, but that is no longer the case.
HIV Medications or “antiretrovirals” (ARVs)
- Antiretrovirals that interact with birth control: There is a risk of interaction with all ARVs.
- Antiretrovirals that don’t interact with birth control: The good news is that there are some safe contraception-ARV combinations. Your doctor can make recommendations on a case-by-case basis.
- Safest contraception options: In most cases, the birth control shot (Depo-Provera), hormonal IUD (eg. Mirena, Kyleena), and copper IUD are all safe to use on HIV treatment. Non-hormonal methods are another safe alternative.
St. John’s Wort
St. John’s Wort (Hypericum perforatum), an herbal supplement sometimes used to treat symptoms of depression, may mess with your hormonal birth control.
I need to take these medications. What are my options?
If you are already on hormonal birth control and are about to start taking one of these medications, your doctor will discuss birth control options with you to make sure your medications don’t interact. The birth control shot, IUD, or implant may be your best bet.
If you are interested in starting hormonal birth control, be sure to let your doctor know about your existing prescriptions. If your are taking one of the medications above and decide to stop, be aware that it could take up to 28 days after stopping before any hormonal birth control will be fully effective. In the meantime, you will need backup contraception.
Either way, your prescriber will be able to advise you on the safest birth control for you depending on what other meds you take or are about to start.
Will emergency contraception Plan-B work if I am on these medications?
Emergency contraception Plan-B may not work if you:
- Weigh over 165 pounds
- Take anti-seizure medications, antibiotics for TB, HIV medications, or St. John’s Wort
- Have recently used anti-seizure medications, antibiotics for TB, HIV medications, or St. John’s Wort
In these cases, the best method of emergency contraception is the copper IUD, for example, ParaGard. This will need to be inserted by a trained healthcare professional within 5-7 days of having unprotected sex. For more information about emergency contraception, see our blog post here.
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