Anticonvulsants and Birth Control: What You Need to Know About Reduced Effectiveness

When you're taking medication for seizures, you might not think about how it affects your birth control. But for women using anticonvulsants, this interaction isn't just a footnote-it's a serious risk. Studies show that some common seizure medications can cut the effectiveness of oral contraceptives by up to 60%. That means even if you take your pill every day, perfectly, you could still get pregnant. And this isn't rare. Around 1.2 million women in the U.S. are caught in this gap between neurology and reproductive health, often without ever being warned.

Which Anticonvulsants Really Lower Birth Control Effectiveness?

Not all seizure drugs do this. But the ones that do are some of the most commonly prescribed. Carbamazepine (Tegretol), phenytoin (Dilantin), phenobarbital, primidone, oxcarbazepine (Trileptal), and felbamate (Felbatol) are all strong enzyme inducers. They crank up the liver's ability to break down hormones, which means estrogen and progestin from birth control pills, patches, or rings get flushed out of your system too fast to work.

Topiramate (Topamax) is another one, but only at higher doses. At 200 mg per day, it lowers estrogen levels by about 23%. At 400 mg, that jumps to 43%. That’s not a small drop-it’s enough to make birth control unreliable.

On the flip side, valproate (Depakote), gabapentin (Neurontin), pregabalin (Lyrica), and levetiracetam (Keppra) don’t interfere with hormonal birth control. If you’re on one of these, your pill should still work as expected. But if you’re on carbamazepine or topiramate? You need a different plan.

The Birth Control Methods That Don’t Work Well

Combined hormonal contraceptives-those with both estrogen and progestin-are the most affected. That includes:

• Combined oral contraceptive pills (like Ortho Tri-Cyclen, Yaz, or Loestrin)
• The patch (Ortho Evra)
• The vaginal ring (NuvaRing)

These all rely on steady hormone levels. When your liver starts burning them off faster, your body doesn’t get enough to prevent ovulation. Studies have shown that women on enzyme-inducing anticonvulsants using these methods have a pregnancy rate of up to 5% per year-far higher than the less than 1% rate with perfect use.

Even emergency contraception is risky. Levonorgestrel (Plan B, Next Choice) loses about half its effectiveness. Ulipristal acetate (Ella) may not work at all. If you need emergency birth control and you’re on carbamazepine or topiramate, don’t rely on these. Talk to your doctor about a copper IUD as an emergency option-it works regardless of drug interactions.

What Birth Control Methods Still Work?

Good news: there are safe, effective alternatives that don’t depend on liver metabolism.

• Levonorgestrel IUDs (Mirena, Kyleena): These release progestin directly into the uterus. Studies show pregnancy rates below 0.1% per year-even when taken with enzyme-inducing anticonvulsants.
• Copper IUD (ParaGard): No hormones at all. Works by creating a hostile environment for sperm. Completely unaffected by any medication.
• Depo-Provera (DMPA): The shot gives you 150 mg of progestin every 12-13 weeks. That’s a massive dose. Even if your liver tries to break it down, there’s still enough left to stop ovulation.

Many women who switched from pills to an IUD report better seizure control, fewer breakthrough bleeds, and peace of mind. One woman on Reddit shared: “After switching from birth control pills to Mirena when I started Keppra, my periods became regular and I haven’t had any seizure changes.”

The Lamotrigine Problem: It’s a Two-Way Street

Lamotrigine (Lamictal) is a special case. It doesn’t speed up hormone breakdown. But hormonal birth control speeds up lamotrigine breakdown.

When you take estrogen-containing birth control, your lamotrigine levels drop by about 50%. That’s dangerous. Lower lamotrigine means higher seizure risk. And when you stop the pill for your week off, your lamotrigine levels spike-by 30-40%. That can cause dizziness, blurred vision, or even new seizures.

The fix? Avoid estrogen altogether. Use a progestin-only method like the IUD or the shot. If you must use a combined pill, your neurologist may need to raise your lamotrigine dose by 50-100%. But that’s not simple. Dose changes need careful monitoring with blood tests. Extended-cycle pills (taking active pills for 84 days straight) can help avoid the hormone drop that triggers lamotrigine spikes.

Why This Isn’t Just a ‘Birth Control’ Issue

Unplanned pregnancy in women with epilepsy isn’t just inconvenient-it’s dangerous. Many anticonvulsants are known teratogens. Carbamazepine and valproate, for example, carry a 30-40% higher risk of major birth defects than the general population’s 2-3% baseline. The NEAD Registry found that women on enzyme-inducing drugs have a 6-10% chance of having a baby with a major malformation.

That’s why preventing unintended pregnancy isn’t just about avoiding a baby-it’s about protecting the baby you might have. It’s also about protecting yourself. Seizure frequency often increases during pregnancy. And if you’re not planning it, you might be taking high-risk meds during early pregnancy before you even know you’re pregnant.

What Doctors Aren’t Telling You

A 2022 survey by the Epilepsy Foundation found only 35% of women with epilepsy received contraceptive counseling from their neurologist. Only 22% got it from their gynecologist. That’s a massive gap.

One woman wrote on Reddit: “I got pregnant on Ortho Tri-Cyclen while taking Tegretol despite perfect use-my neurologist never warned me about the interaction.”

The American College of Obstetricians and Gynecologists (ACOG) says doctors should be talking about this at every visit. The CDC classifies combined hormonal contraceptives as Category 3 for women on enzyme-inducing anticonvulsants-meaning the risks usually outweigh the benefits. Yet many women still get prescriptions for them without a word.

What You Should Do Right Now

If you’re taking any anticonvulsant and using hormonal birth control:

1. Check which drug you’re on. Is it carbamazepine, topiramate, phenytoin, or another enzyme inducer?
2. Look at your birth control method. Is it a pill, patch, or ring?
3. If both are true, you’re at risk. Don’t wait for your next appointment. Call your neurologist and gynecologist together.
4. Ask: “Is my birth control still working with my seizure meds?”
5. Request a copper IUD or levonorgestrel IUD. They’re safe, long-lasting, and don’t need daily attention.
6. If you’re on lamotrigine, avoid estrogen. Ask about non-hormonal options or dose adjustments.
7. Never use Plan B or Ella as emergency contraception if you’re on enzyme inducers. Go straight to a clinic for a copper IUD.

The Future Is Changing

Newer anticonvulsants like perampanel (Fycompa) and brivaracetam (Briviact) don’t induce liver enzymes. That makes them safer for women who need reliable contraception. More doctors are starting to switch patients to these when possible.

The NIH is tracking 5,000 pregnancies to better understand how different drugs affect birth outcomes. And the Gates Foundation is funding research into a non-hormonal contraceptive gel that’s showing 99% effectiveness in animals-potentially eliminating this entire problem in the future.

But for now, the solution is simple: know your drugs. Know your birth control. Ask the hard questions. And don’t assume your doctor already told you everything you need to know.