What Medications Interfere With Birth Control Pills?

Some medications don’t play nicely together. One might make the other less effective. For example, you may use hormonal contraceptives (birth control). If you need another medication for an illness or health condition, you may wonder if the medicine will affect how well your birth control works.

Most people don’t need to worry about medications interacting with their birth control, says Ob/Gyn Emily Freeman, DO. She explains what medications may affect birth control, however, and how to avoid any problems.

Medications and your birth control

Hormonal contraceptives contain a combination of estrogen and progestin or just progestin hormones that can help prevent pregnancy in several ways, like:

• Preventing ovulation (monthly release of an egg).
• Keeping sperm from reaching an egg.

But if you’re taking a medication that interferes with those hormones, your contraception can’t do its job.

“Most medications we prescribe don’t interact with contraception,” clarifies Dr. Freeman. “But there are some medications that can disrupt certain types of birth control — specifically, combined hormonal contraception (CHC) such as oral contraceptives (‘the pill’), vaginal rings and birth control patches.”

CHCs contain both estrogen and progestin.

How medications and birth control interact

The most common way a medication interacts with CHCs is through your liver’s cytochrome P450 enzymes. These enzymes control:

• How quickly drugs are metabolized or broken down.
• How long they stay active in your body.

“Taking medication and birth control that both interact with cytochrome P450 enzymes can cause your body to metabolize birth control more quickly,” explains Dr. Freeman. “The enzymes rapidly clear the hormonal contraception from your body.”

Without these hormones, you may be at risk of pregnancy.

What medications affect birth control?

Most prescribed and over-the-counter medications won’t interact with hormonal birth control. But certain classes of drugs — associated with specific conditions — are known to affect CHCs:

1. Seizure medication and birth control

Anti-epileptic drugs (AEDs) work to prevent or stop seizures — temporary bursts of electrical activity in the brain that cause symptoms such as uncontrollable muscle movements and abnormal sensations.

“Drugs used to treat seizures are most likely to interact with CHCs,” Dr. Freeman shares. “Many of the AEDs we use today don’t interfere. But there are still some AEDs prescribed that may affect your birth control.”

Commonly prescribed AEDs that can make hormonal birth control less effective include:

• Carbamazepine, also used to treat schizophrenia, restless legs syndrome, bipolar disorder and neuropathic pain associated with fibromyalgia.
• Phenytoin, also used to treat behavior disorders and neuropathic pain.
• Topiramate, also used to treat neuropathic pain, eating disorders, psychiatric disorders and migraine headaches.

Dr. Freeman also notes that one other AED, lamotrigine, interacts with CHCs. But in this case, lamotrigine is the drug affected. Taking CHCs can make lamotrigine less effective in treating seizures.

2. Anti-HIV drugs and birth control

Some anti-HIV drugs, called antiretrovirals (ARVs), make birth control less effective. But Dr. Freeman notes the opposite can also happen — some types of CHCs can decrease the effectiveness of ARVs.

Research shows some concern about several ARVs, but only efavirenz proved to have a significant impact on hormonal birth control. Experts suggest that more studies are needed to confirm additional drug interactions.

“The development of HIV medications is rapidly changing,” Dr. Freeman says. “So, if you’re taking medicine for HIV, check in with your healthcare provider to make sure there are no concerns about a potential interaction.”

3. Antibiotics and birth control

Most antibiotics don’t interact with birth control pills or other CHCs.

“Using birth control pills and antibiotics simultaneously is typically not going to affect either medication,” Dr. Freeman clarifies. “But there is one antibiotic that causes concern for people taking birth control pills.”

Rifampin, used to treat tuberculosis, is a rarely prescribed antibiotic that makes hormonal birth control less effective. A typical course of tuberculosis treatment is six to nine months. When using rifampin, use an alternate method of contraception.

4. Herbal supplements and birth control

Herbal supplements come from all parts of plants, and many are thought to have healing properties. But these herbal treatments may interact with medications.

Supplements aren’t evaluated by the U.S. Food and Drug Administration (FDA), so research is limited. Experts don’t know how most supplements interact with hormonal contraceptives. But researchers have studied St. John’s wort — an herbal supplement often used to treat depression, menopausal symptoms and attention-deficit/hyperactivity disorder (ADHD). Research links St. John’s wort with breakthrough bleeding and quicker metabolism of the hormones in CHCs.

“Experts believe St. John’s wort may decrease the effectiveness of hormonal birth control,” Dr. Freeman adds. “But other medications used to treat depression and anxiety generally don’t affect birth control.”

Tips for avoiding drug interactions with birth control

If you’re taking hormonal birth control and prescription medication, safeguard yourself against possible drug interactions:

• Make sure your medication list is up to date. Let your healthcare provider know when you start or stop a medication to prevent and identify possible drug interactions.
• Read the insert for prescription medications. If you have any reason to suspect a possible drug interaction, talk to your provider before taking the medication.

“When in doubt, use a backup method of birth control,” advises Dr. Freeman. “Reach out to your healthcare provider to see if an alternative method of birth control or different medication might be a better fit.”