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Medications That Make Birth Control Less Effective

The 1 Thing You Should Ask Your Doctor Before Mixing Birth Control With Other Medications

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It's easy to forget that there are risks involved with mixing medications, especially when one is a routine pill like birth control. But did you know that some medications can actually make your birth control less effective? We asked Harpreet Brar, MD, a board certified ob-gyn at Detroit Medical Centre's Hutzel Women's Hospital, for a complete rundown.

Which Medications Interfere With Birth Control?

There are a few fairly common medications that can mess with hormonal contraceptives, specifically the pill and any IUD containing levonorgestrel (a type of progestin), according to Dr. Brar.

  • Medications for seizure disorders: These drugs, including the common one, Topamax, increase the breakdown of the hormones in your birth control pill, which makes it less useful.
  • Antifungal medications: "Antifungal medications can increase the serum [blood] concentration of hormonal birth controls by inhibiting the enzyme CYP3A4, which is important in the breakdown of progestin hormones," Dr. Brar said. Griseofulvin and ketocanazolen are ones to watch out for.
  • The antibiotic rifampin: "Rifampin affects oral birth control pills by increasing the activity of cytochrome P450, which is involved in breaking down estrogen. This decreases estrogen levels and the overall effectiveness of estrogen in oral birth control pills," Dr. Brar said.
  • Antiretroviral medications for HIV: Some but not all of these can throw off your cycle, potentially interfering with your birth control, so ask your doctor before starting any of them.

"The over-the-counter supplement St John's wort may also interfere with common birth control," she added.

What Should You Do If You're Prescribed One of These Meds?

Always remind your doctor that you're on birth control any time they mention starting a new medication. While your physician probably already knows this, you should get reassurance that they've considered any potential interactions before you pick up your 'scrip from the pharmacy. Dr. Brar said that, in most cases, an alternative to these medications can be prescribed that won't interfere with your birth control.

If that's not the case, your doctor will suggest that you use a second form of contraception. "When in doubt, a backup method of contraception such as condoms should be utilized," Dr. Brar said, though your doctor should be able to tell you how soon after treatment your birth control will become effective again. If you're on a longer course of treatment, you might also consider switching birth controls instead, to a nonhormonal method like the copper IUD.

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