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

Many women taking medication for epilepsy or other seizure disorders rely on birth control pills, patches, or rings to prevent pregnancy. But what if those same medications are quietly making their birth control less effective? This isn’t a rare edge case-it’s a well-documented, clinically significant interaction that affects over a million women in the U.S. alone. If you’re on anticonvulsants and using hormonal contraception, you need to know the real risks-and what actually works.

Which Anticonvulsants Are the Problem?

Not all seizure medications interfere with birth control. But several common ones do-and they do it aggressively. These are called enzyme-inducing antiepileptic drugs (EIAEDs). They trigger your liver to produce more of a specific group of enzymes (CYP450) that break down hormones faster than normal. That means estrogen and progestin from your pill, patch, or ring get flushed out of your system before they can do their job.

The big offenders include:

• Carbamazepine (Tegretol)
• Oxcarbazepine (Trileptal)
• Phenytoin (Dilantin)
• Phenobarbital
• Primidone (Mysoline)
• Topiramate (Topamax)-especially at doses above 200 mg/day
• Felbamate (Felbatol)

Studies show these drugs can slash estrogen levels by up to 60% and progestin by half. For example, women taking topiramate at 400 mg/day had 43% lower estrogen levels compared to those not on anticonvulsants. That’s not a small drop-it’s enough to leave you unprotected.

What Birth Control Methods Are Affected?

If you’re using any method that relies on hormones your liver can break down, you’re at risk:

• Combined oral contraceptive pills (COCs)
• The contraceptive patch (Ortho Evra)
• The vaginal ring (NuvaRing)

These all deliver estrogen and/or progestin that get metabolized by the same liver enzymes your anticonvulsants are overactivating. Even if you take your pill at the same time every day, it won’t matter if your body is destroying the hormones before they can act.

Emergency contraception is also compromised. Levonorgestrel (Plan B, Next Choice) loses about half its effectiveness. Ulipristal acetate (Ella) may not work at all. If you need emergency contraception while on these anticonvulsants, you’re better off with a copper IUD inserted within five days-no hormones involved.

What Birth Control Still Works?

The good news? Several highly effective options don’t rely on liver metabolism and remain fully functional:

• Levonorgestrel IUDs (Mirena, Kyleena): These release progestin directly into the uterus. Studies show pregnancy rates below 0.1% per year-even with enzyme-inducing anticonvulsants.
• Copper IUD (ParaGard): Works without hormones at all. It’s not affected by any drug interaction.
• Depo-Provera (DMPA): The shot delivers 150 mg of progestin every 12-13 weeks. That high dose overwhelms the enzyme activity, so it still works.
• Implant (Nexplanon): While not mentioned in all guidelines, current evidence suggests it remains effective because it delivers a steady, low dose directly under the skin, bypassing first-pass liver metabolism.

These are the gold-standard choices for women on carbamazepine, topiramate, or phenytoin. No guesswork. No extra pills to remember. Just reliable protection.

The Lamotrigine Twist

Lamotrigine (Lamictal) is a common anticonvulsant that doesn’t induce liver enzymes-but it has its own tricky interaction. When you take combined hormonal contraceptives, your body breaks down lamotrigine 50% faster. That means your seizure control can drop, and you might start having more seizures.

And here’s the catch: when you stop taking the pill during your placebo week, lamotrigine levels spike by 30-40%. That can cause dizziness, blurred vision, or even dangerous skin reactions.

So if you’re on lamotrigine, estrogen-containing birth control is risky-not because it fails, but because it makes your seizure meds less effective. The solution? Use progestin-only methods (IUD, implant, shot) or adjust your lamotrigine dose under close supervision. Some doctors increase the dose by 50-100% when starting hormonal contraception-but only if they’re monitoring blood levels.

What About Valproate, Gabapentin, or Keppra?

If you’re on valproate (Depakote), gabapentin (Neurontin), pregabalin (Lyrica), or levetiracetam (Keppra), you’re in the clear. These drugs don’t trigger the liver enzymes that break down birth control hormones. You can safely use pills, patches, or rings without added risk.

But don’t assume your doctor knows this. A 2022 survey found that only 35% of women with epilepsy got contraceptive counseling from their neurologist, and just 22% from their gynecologist. That’s a massive gap. If you’re on one of these safer drugs, still confirm it with your care team. Don’t assume.

Why This Matters Beyond Pregnancy

Unplanned pregnancy isn’t just inconvenient-it’s dangerous for women with epilepsy. Many anticonvulsants are known teratogens. Carbamazepine and phenytoin increase the risk of major birth defects by 30-40% compared to the general population’s 2-3%. Seizures during pregnancy can also harm both mother and baby.

Preventing unintended pregnancy isn’t just about birth control-it’s about protecting your health and your future child’s.

What Should You Do?

If you’re taking any anticonvulsant and using hormonal birth control, here’s your action plan:

1. Identify your medication: Is it carbamazepine, topiramate, phenytoin, or another enzyme inducer? Check your prescription label or ask your pharmacist.
2. Don’t rely on pills, patches, or rings: If you’re on one of the high-risk drugs, these are not safe as your only method.
3. Switch to an IUD or implant: These are the most reliable options. Mirena, Kyleena, ParaGard, and Nexplanon are all proven effective.
4. Ask about lamotrigine: If you’re on lamotrigine, avoid estrogen. Talk to your doctor about dose adjustments or switching to progestin-only methods.
5. Use backup condoms: If you’re stuck with a hormonal method for now, use condoms every time until you can switch to a safer option.
6. Get counseling: Request a joint appointment with your neurologist and gynecologist. They need to talk to each other to get this right.

The Bigger Picture

This isn’t just about individual choices-it’s a systemic failure. The FDA requires drug labels to warn about these interactions. Tegretol’s package insert clearly says: “Contraceptives containing estrogen or progestin may be ineffective when used concurrently with Tegretol.” Yet, most women still aren’t warned.

Researchers are working on solutions. Newer anticonvulsants like perampanel (Fycompa) and brivaracetam (Briviact) don’t induce liver enzymes, making them better options for women of childbearing age. Non-hormonal contraceptives are also in development, including a promising gel backed by the Gates Foundation.

But right now, the safest, most effective path is clear: switch to a non-interacting method. Your body doesn’t need to be a battlefield between your seizure meds and your birth control. There are better options. You just need to ask for them.