Morning After Pill Drug Interactions: What to Avoid and What to Tell Your Doctor

Before taking Plan B or ella, it is important to know whether any medications or supplements you are taking could interfere with how well they work. Certain drugs—including some common medications for seizures, infections, and even an herbal supplement—can significantly reduce the effectiveness of emergency contraception. Here is what you need to know.

Why Do Some Drugs Reduce Emergency Contraception Effectiveness?

Both levonorgestrel (Plan B) and ulipristal acetate (ella) are processed by the body's CYP3A4 enzyme system in the liver. Drugs that speed up this enzyme system—called CYP3A4 inducers—cause the body to break down these contraceptives faster. Lower drug levels mean lower effectiveness, which means a higher risk of pregnancy.

Medications That Reduce Plan B (Levonorgestrel) Effectiveness

The following medications and supplements can reduce the effectiveness of Plan B and other levonorgestrel emergency contraceptives:

• Rifampin (Rifadin): An antibiotic used to treat tuberculosis (TB) and other serious infections. This is one of the most significant interactions—rifampin substantially reduces levonorgestrel blood levels.
• Griseofulvin (Gris-PEG): An antifungal medication. Note that other common antifungals (fluconazole, clotrimazole, etc.) do NOT interact with Plan B.
• St. John's Wort: A widely used herbal supplement for mood support. St. John's wort is a CYP3A4 inducer and reduces levonorgestrel levels significantly. If you take St. John's wort regularly, Plan B may not be effective for you.
• Efavirenz: An HIV antiretroviral medication. Reduces levonorgestrel efficacy; the copper IUD is the recommended option for patients on efavirenz.
• Some anti-seizure medications: Carbamazepine (Tegretol), phenytoin (Dilantin), topiramate (Topamax), oxcarbazepine (Trileptal), primidone (Mysoline), and phenobarbital reduce the effectiveness of both Plan B and ella.

Medications That Reduce Ella (Ulipristal Acetate) Effectiveness

Ella has additional interactions beyond those affecting Plan B:

• Hormonal birth control (pills, patch, ring, injection, implant): Progestins in hormonal contraceptives bind to the same receptors as ella and can reduce ella's effectiveness. Wait at least 5 days after taking ella before restarting hormonal birth control, and use barrier contraception in the meantime.
• Bosentan: A medication used for pulmonary arterial hypertension (PAH) that may reduce ella's effectiveness.
• Grapefruit juice: Grapefruit and grapefruit juice affect CYP3A4 enzyme activity and should be avoided while taking ella.

What to Do If You Take an Interacting Medication

If you are taking any of the medications listed above and need emergency contraception, the recommended alternative is the copper IUD (Paragard). Because the copper IUD works through a hormonal-independent mechanism (copper is directly toxic to sperm), its effectiveness is NOT reduced by any of the medications listed above. It is more than 99% effective when placed within 5 days of unprotected sex, regardless of what other medications you are taking.

If the copper IUD is not available or not preferred, contact your healthcare provider or pharmacist immediately for personalized guidance. In some situations, a higher dose of levonorgestrel may be considered, though this is an off-label approach and should only be used with medical guidance.

Common Medications That Do NOT Interact With Plan B

Patients often worry about interactions that do not actually exist. To be clear, the following medications are NOT known to significantly reduce Plan B effectiveness:

• Most common antibiotics (amoxicillin, azithromycin, doxycycline, ciprofloxacin) — only rifampin interacts with Plan B
• Most antifungals (fluconazole/Diflucan, clotrimazole) — only griseofulvin interacts
• Common pain relievers (ibuprofen, acetaminophen, naproxen)
• Most antidepressants (SSRIs, SNRIs) — no significant interaction with Plan B

Tell Your Pharmacist or Doctor Before Taking EC

Whenever possible, let your pharmacist or healthcare provider know all current medications, including herbal supplements, before taking emergency contraception. They can quickly flag any interactions and guide you to the most effective option. For information about side effects, see morning after pill side effects. Need to find a pharmacy near you? medfinder can help you locate one with the medication in stock.