Norgestrel Drug Interactions: What to Avoid and What to Tell Your Doctor

Norgestrel (Opill) is an over-the-counter progestin-only birth control pill. Although it doesn't require a prescription, it can still interact with other medications — and some of those interactions can reduce its effectiveness at preventing pregnancy. If you take any prescription drugs, supplements, or herbal remedies, it's important to know which ones might be a problem.

This guide covers the most clinically significant interactions with norgestrel — what they are, why they happen, and what to do about them.

How Drug Interactions with Norgestrel Work

Most drug interactions with norgestrel involve liver enzymes — specifically a group of enzymes called CYP3A4. Your liver uses CYP3A4 to break down and eliminate norgestrel from your body. Some drugs or supplements speed up these enzymes (called "inducers") — causing norgestrel to be eliminated faster, which lowers its blood levels and reduces contraceptive effectiveness. Others slow these enzymes down ("inhibitors"), raising norgestrel levels in your blood.

Category 1: Drugs That REDUCE Norgestrel Effectiveness (CYP3A4 Inducers)

These are the most important interactions to know — they can make norgestrel less effective at preventing pregnancy:

• Carbamazepine (Tegretol): An antiseizure and mood-stabilizing medication. A moderate CYP3A4 inducer that can lower norgestrel levels. Use backup contraception or consider a different birth control method.
• Phenytoin (Dilantin) and phenobarbital: Antiseizure medications that induce CYP3A4 and can reduce progestin levels.
• Rifampin (Rifadin): An antibiotic used to treat tuberculosis and other infections. It is a strong CYP3A4 inducer and can significantly reduce hormonal contraceptive effectiveness.
• Apalutamide (Erleada): A prostate cancer medication that is a strong CYP3A4 inducer. Avoid norgestrel and use a non-hormonal contraceptive while on this drug. Continue backup contraception for 28 days after stopping apalutamide.
• Topiramate (Topamax): Used for seizures and migraines. Can reduce progestin levels at higher doses.
• Bosentan (Tracleer): Used for pulmonary arterial hypertension. A moderate CYP3A4 inducer that can reduce norgestrel concentrations.

Category 2: Herbal Supplements That Reduce Norgestrel Effectiveness

• St. John's Wort (Hypericum perforatum): One of the most clinically significant herbal interactions. St. John's Wort is a CYP3A4 inducer and can significantly reduce the effectiveness of norgestrel and other hormonal contraceptives. If you take St. John's Wort for depression, talk to your provider about non-hormonal contraception or a different antidepressant.

Category 3: Drugs That INCREASE Norgestrel Levels (CYP3A4 Inhibitors)

These drugs slow down the enzymes that break down norgestrel, potentially increasing its blood levels. Higher levels don't necessarily improve contraceptive effectiveness and may increase the risk of side effects:

• Ritonavir (Norvir) and nirmatrelvir/ritonavir (Paxlovid): Used to treat HIV and COVID-19. Strong CYP3A4 inhibitors. Monitor for increased norgestrel side effects (such as irregular bleeding) if taking these medications. Consult your provider.
• Ketoconazole, itraconazole (antifungals): CYP3A4 inhibitors that may increase norgestrel concentrations when used concurrently. Monitor for side effects.

Category 4: Emergency Contraceptive Interaction — Ulipristal Acetate (Ella)

This is a critical interaction unique to progestin-based contraceptives:

Do not take norgestrel within 5 days of taking ulipristal acetate (Ella). Ulipristal works by blocking progesterone receptors — the same receptors norgestrel needs to work. Taking norgestrel too soon after Ella can make both drugs less effective. The FDA advises waiting at least 5 days after ulipristal before starting norgestrel, and using a barrier method during that time.

Category 5: Other Hormonal Contraceptives

Do not use norgestrel simultaneously with other hormonal contraceptives — the pill, patch, ring, injectable, implant, or hormonal IUD. Combining methods does not improve effectiveness and can cause hormonal imbalances. If you're switching methods, ask your provider for guidance on the correct timing to maintain continuous protection.

Do Antibiotics Affect Norgestrel?

With one exception (rifampin), most commonly prescribed antibiotics do not significantly reduce the effectiveness of norgestrel or other hormonal contraceptives. The old advice to use backup contraception during any antibiotic course is no longer considered necessary for most antibiotics by current FDA and ACOG guidance. However, if your doctor prescribes rifampin or rifabutin, use backup contraception.

What to Tell Your Doctor or Pharmacist

Even though Opill is OTC, it's important to tell your healthcare provider and pharmacist that you are taking it. Bring this information to every appointment and whenever you are prescribed a new medication. Key things to mention:

• "I am taking norgestrel (Opill) 0.075 mg daily for contraception"
• Tell them about all supplements including St. John's Wort, which is often not mentioned because it's herbal
• Ask whether any newly prescribed medication could reduce norgestrel's effectiveness

Also see: Norgestrel side effects: What to expect and when to call your doctor.

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