Do Antibiotics Affect Birth Control?

Antibiotics are commonly prescribed for infections every day in the U.S.

Like many medications, antibiotics have the potential to interact with other medications in different ways, so it’s important to talk with your primary care provider before you start taking them.

There are misconceptions about how other medications may affect the birth control pill. Tara Gellasch, MD, works as an OBGYN at our UMMC Women’s Care office in Batavia, and explains how antibiotics and birth control function.

How birth control works

The most commonly used form of birth control is in pill form. These pills are a combination of estrogen and progesterone, or a ‘mini pill’ containing progesterone alone.

For a birth control pill to be effective, a woman has to take the pill every day. The hormones are quickly processed by the body, which includes passing through the liver.

Do antibiotics change how birth control works?

Certain medications can affect how quickly the liver processes the hormones, which can change the effectiveness of the pill. However, antibiotics used to treat common illnesses like bladder infections, sexually transmitted infections, ear infections, and pneumonia do not alter the effectiveness of the pill.

Only one antibiotic has been shown to increase the metabolism of the liver, and thus to decrease the amount of hormone in a woman’s body: rifampin.

Rifampin is used to treat tuberculosis and meningococcal carriers – both of which are rare in the United States.

“Even though antibiotics don’t affect how effective birth control is, it is very important to continue to take the pill at the same time each day – even when you are sick,” Dr. Gellasch said. “If nausea and/or vomiting makes it impossible to keep your poll down, be sure to use a backup method of birth control.”

Ask a healthcare provider how long you should be using a backup method; everyone’s situation is different.

Other common medications affecting liver function

Some common medications that can increase the liver’s activity are actually anti-seizure or anti-convulsant medications. These medications can decrease the effectiveness of the birth control pill and increase the risk of an unplanned pregnancy. Women taking any of the below list of medications should speak to their medical provider before relying solely on a birth control pill for contraception:

• barbiturates
• carbamazepine (tegretal)
• oxcarbazepine (trileptal)
• phenytoin (Dilantin)
• primidone
• topiramate (Topamax)

Women who take these medications and use the pill as contraception will not experience harmful effects, but the pill’s effectiveness may be decreased, increasing the chances of an unplanned pregnancy.

There are other effective methods of birth control for these women, including:

• depo-provera
• intrauterine devices (IUDs)
• Nexplanon

Birth control pills may actually reduce the effectiveness of the anticonvulsant lamotrigine (lamictal) by increasing the liver’s clearance of that medication. Anti-convulsant medications that do not seem to affect the birth control pill include gabapentin (Neurontin), levetriacetam (keppra), and tiagabine.

“There are definitely many long-held beliefs that antibiotics affect birth control,” Dr. Gellasch said. “The facts are that the only antibiotic that decreases the effectiveness of the birth control pill is rifampin, which is not commonly used.”