Anticonvulsants and Oral Contraceptives: How Seizure Medications Can Reduce Birth Control Effectiveness

By Joe Barnett On 24 Dec, 2025 Comments (9)

Anticonvulsant Birth Control Safety Checker

Check if your seizure medication affects the effectiveness of your birth control method. Select your medication and birth control method below to see if you need to consider alternative options.

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When you're taking medication for seizures, the last thing you should worry about is accidentally getting pregnant. But for many women, that’s exactly what happens - not because they missed a pill, but because their seizure medication is quietly breaking down their birth control. This isn’t rare. It’s a well-documented, under-discussed interaction that puts thousands of women at risk every year.

How Anticonvulsants Break Down Birth Control

The problem starts in your liver. Certain anticonvulsants - like carbamazepine (Tegretol), phenytoin (Dilantin), oxcarbazepine (Trileptal), and topiramate (Topamax) - are called enzyme-inducing antiepileptic drugs (EIAEDs). These drugs crank up the activity of liver enzymes, specifically the CYP450 system, which is responsible for breaking down chemicals in your body.

That’s great if you’re trying to clear toxins. But when those same enzymes start chewing up the hormones in your birth control pill, patch, or ring, the result is simple: your body never gets enough estrogen or progestin to stop ovulation. Studies show these drugs can slash ethinyl estradiol levels by up to 60% and progestin by as much as 50%. That’s not a small drop - it’s enough to make hormonal birth control useless.

Topiramate is especially tricky. At doses above 200 mg per day, it reduces estrogen levels by 23%. At 400 mg, that jumps to 43%. And most women don’t even realize their dose has crossed that threshold. They’re just taking what their neurologist prescribed.

Which Birth Control Methods Are Most at Risk?

If you’re using a pill, patch, or vaginal ring - all of which rely on liver-metabolized hormones - you’re in the danger zone. The patch and ring are especially risky because they’re designed to release steady doses, and even a 30% drop in hormone levels can throw off the entire system.

Emergency contraception isn’t safe either. Levonorgestrel (Plan B) loses about half its effectiveness when taken with enzyme-inducing anticonvulsants. Ulipristal acetate (Ella) may not work at all. That means if you need emergency contraception after unprotected sex, you can’t rely on what’s in your medicine cabinet.

What about the IUD? That’s where things get better. The levonorgestrel IUDs - Mirena and Kyleena - still work. Their progestin is released directly into the uterus, bypassing the liver entirely. The copper IUD (ParaGard) is completely unaffected because it doesn’t use hormones at all. These are the two safest, most reliable options for women on enzyme-inducing anticonvulsants.

Depo-Provera Is Still an Option

The shot - depot medroxyprogesterone acetate (DMPA) - also remains effective. Even though it’s a hormone, it’s given as a 150 mg injection every 12 to 13 weeks. That high, slow-release dose overwhelms the liver’s ability to break it down. Women on carbamazepine or phenytoin who use Depo-Provera have pregnancy rates under 1% per year, matching the general population.

But there’s a catch: Depo-Provera can cause bone density loss with long-term use. It’s not ideal for younger women who plan to have children in the next few years. Still, for those who need a low-maintenance, reliable method, it’s a solid choice - if you’re okay with the side effects.

Medical diagram showing hormonal birth control being broken down by liver enzymes, while IUDs remain unaffected.

The Lamotrigine Problem

Lamotrigine (Lamictal) is one of the most common anticonvulsants used today. But here’s the twist: it doesn’t reduce birth control effectiveness. Instead, birth control reduces lamotrigine’s effectiveness.

Combined hormonal contraceptives can cut lamotrigine levels in half. That’s dangerous. If your seizure medication drops too low, you could have a breakthrough seizure - even if you’ve been stable for years. And when you stop taking the pill during your placebo week, lamotrigine levels spike by 30-40%, raising the risk of dizziness, rash, or worse.

This bidirectional interaction makes lamotrigine one of the trickiest combinations to manage. The solution? Avoid estrogen-containing birth control. Use a progestin-only pill, IUD, or implant. Or, if you must use a combined method, your neurologist may need to increase your lamotrigine dose by 50-100%. But that requires close monitoring - blood tests, seizure logs, and regular check-ins.

Safe Alternatives for Women on Anticonvulsants

Not all anticonvulsants interfere with birth control. Valproate (Depakote), gabapentin (Neurontin), pregabalin (Lyrica), and levetiracetam (Keppra) don’t trigger liver enzyme changes. That means if you’re on one of these, standard birth control pills, patches, or rings are generally safe.

But here’s the problem: most women aren’t told this. A 2022 survey by the Epilepsy Foundation found that only 35% of women with epilepsy received contraceptive counseling from their neurologist. Only 22% heard it from their gynecologist. That’s a massive gap. Many women are left guessing - and paying the price.

Real stories prove it. One woman on Reddit shared: “I got pregnant on Ortho Tri-Cyclen while taking Tegretol - my neurologist never warned me.” Another wrote: “Switched from pills to Mirena when I started Keppra. My periods became regular. No seizures changed.”

What the Experts Say

The American College of Obstetricians and Gynecologists (ACOG) calls combined hormonal contraceptives a Category 3 risk for women on enzyme-inducing anticonvulsants. That means the risks usually outweigh the benefits. The CDC agrees.

ACOG’s official recommendation? Use a copper IUD or a levonorgestrel IUD. If you want a shot, go with Depo-Provera. If you’re set on pills, use one with at least 50 mcg of ethinyl estradiol - but know that even that isn’t foolproof. Always use condoms as backup.

For lamotrigine users: avoid estrogen. Use progestin-only methods. Adjust your dose under medical supervision. Don’t stop your seizure meds. Don’t stop your birth control without talking to both your neurologist and your gynecologist.

Woman consulting two doctors, holding an IUD as glowing light contrasts with dissolving birth control pills.

Why This Matters More Than You Think

Unplanned pregnancies in women with epilepsy come with extra risks. Many anticonvulsants - especially carbamazepine and phenytoin - are linked to birth defects. The risk of major congenital malformations is 30-40% higher than in the general population. That’s why preventing pregnancy isn’t just about avoiding an unplanned baby - it’s about protecting a future child from serious health problems.

And it’s not just about pregnancy. Women who have seizures during pregnancy are more likely to have complications: preterm labor, low birth weight, even maternal death. Stable seizure control before and during pregnancy saves lives.

What You Should Do Right Now

If you’re on any anticonvulsant and using hormonal birth control, here’s what to do:

Check which drug you’re taking. Is it carbamazepine, phenytoin, oxcarbazepine, topiramate, phenobarbital, felbamate, or primidone? If yes, your birth control is likely compromised.
Don’t panic. Switching methods is safe and effective.
Ask your neurologist: “Is my seizure medication known to interfere with birth control?”
Ask your gynecologist: “What’s the safest birth control option for me right now?”
Consider a copper IUD or levonorgestrel IUD. They’re the most reliable.
If you’re on lamotrigine, avoid estrogen-containing methods unless your dose is adjusted and monitored.
Use condoms as backup if you’re still using pills, patches, or rings.

Don’t wait for your next appointment. If you’ve had breakthrough bleeding, missed a period, or had unprotected sex, get tested. And if you’re planning to get pregnant - talk to your doctors now. Preconception counseling can change everything.

What’s Changing in the Future

Newer anticonvulsants like perampanel (Fycompa) and brivaracetam (Briviact) don’t trigger liver enzyme changes. They’re becoming popular choices for women of childbearing age - not just because they’re effective for seizures, but because they play nice with birth control.

Research is also moving toward non-hormonal options. The Bill & Melinda Gates Foundation is funding a new contraceptive gel that works without hormones and showed 99% effectiveness in animal trials. If it works in humans, it could be a game-changer.

But for now, the safest, most proven path is simple: know your drugs. Know your options. Talk to both your neurologist and your gynecologist. And never assume your birth control is working just because you’ve never missed a pill.

Can I still use the birth control pill if I take carbamazepine?

It’s not recommended. Carbamazepine reduces hormone levels in birth control pills by up to 60%, making them unreliable. Even high-dose pills (50 mcg ethinyl estradiol) aren’t fully effective. Use an IUD, Depo-Provera, or condoms with the pill as backup.

Does the birth control patch work with anticonvulsants?

No. The patch delivers hormones through the skin, but they still go through the liver. Enzyme-inducing anticonvulsants break them down just like pills. Studies show the patch fails at similar rates to oral contraceptives in women taking carbamazepine or phenytoin.

Is the IUD safe if I take lamotrigine?

Yes. Both the copper IUD and the levonorgestrel IUD (Mirena, Kyleena) are safe. They don’t interfere with lamotrigine levels. In fact, switching to an IUD is often the best choice for women on lamotrigine because it removes the risk of hormonal fluctuations that can trigger seizures.

Can I use Plan B if I’m on Tegretol?

Plan B (levonorgestrel) is only about half as effective when taken with enzyme-inducing anticonvulsants like Tegretol. It’s not reliable. If you need emergency contraception, talk to your doctor about a higher-dose option or a copper IUD, which is the most effective emergency method.

Why didn’t my doctor tell me about this?

Many doctors don’t know the details. A 2022 survey found only 35% of neurologists routinely discuss birth control with female patients. It’s not negligence - it’s a gap in training. Don’t wait for them to bring it up. Ask. Be your own advocate.

What if I want to get pregnant someday?

Talk to your neurologist and OB-GYN now. Some anticonvulsants increase the risk of birth defects. Planning ahead lets you switch to safer medications before conception. Folic acid supplements, seizure control, and medication adjustments can reduce risks dramatically.