Nortrel 1/35 21 Day Drug Interactions: What to Avoid and What to Tell Your Doctor

Nortrel 1/35 21 Day is generally safe, but certain medications and supplements can interfere with how it works or increase the risk of side effects. Some interactions reduce its effectiveness as a contraceptive — meaning you could become pregnant even while taking the pill correctly. Others can be dangerous in combination. This guide covers the most important drug interactions to know.

Category 1: Drugs That Reduce Contraceptive Effectiveness (Enzyme Inducers)

Some medications speed up the breakdown of hormones in your liver and intestines. This lowers the levels of norethindrone and ethinyl estradiol in your blood, potentially allowing ovulation to occur — reducing the pill's effectiveness. Always use backup contraception (condoms) if you're taking these medications.

Rifampin (rifampicin) — An antibiotic used for tuberculosis and other infections. One of the most significant inducers. Strongly reduces OCP effectiveness. Discuss an alternative contraceptive method with your doctor.

Antiepileptic drugs (AEDs) — Phenytoin (Dilantin), carbamazepine (Tegretol), phenobarbital, oxcarbazepine (Trileptal), topiramate (Topamax), and primidone can reduce OCP hormone levels. If you take an AED, ask your neurologist about non-enzyme-inducing alternatives (like levetiracetam or valproate) and use backup contraception.

HIV antiretrovirals — Certain HIV medications including ritonavir, lopinavir/ritonavir, efavirenz, and some other protease inhibitors and NNRTIs can decrease OCP hormone levels. Discuss your HIV regimen with your provider and use barrier methods as additional contraception.

Modafinil (Provigil) — A medication for narcolepsy and excessive sleepiness. Can reduce estrogen levels. Use backup contraception and consider alternative contraceptive methods.

Aprepitant (Emend) — An anti-nausea medication used during chemotherapy. Can temporarily reduce hormone levels. Use backup contraception during treatment and for 1 month after the last dose.

Category 2: Contraindicated Combinations (Do Not Use Together)

These drug combinations are contraindicated with Nortrel 1/35 21 Day — they can cause serious harm and should not be used together:

Ombitasvir/paritaprevir/ritonavir (Viekira Pak) ± dasabuvir — A Hepatitis C drug combination. Concurrent use with ethinyl estradiol-containing pills causes significant ALT (liver enzyme) elevations. This combination is contraindicated. Switch to a progestin-only pill or non-hormonal contraceptive during Hepatitis C treatment.

Category 3: Drugs Whose Effects Are Changed by Nortrel 1/35 21 Day

Nortrel 1/35 21 Day can also change how other medications work in your body:

Aromatase inhibitors (anastrozole, exemestane, letrozole) — Used for breast cancer treatment. Estrogens from OCPs counteract the effects of aromatase inhibitors. These medications should not generally be used together.

Thyroid medications — Estrogens increase levels of thyroid-binding globulin (TBG), which can affect thyroid hormone levels. Patients on thyroid replacement therapy (levothyroxine) may need dose adjustments when starting or stopping OCPs.

Warfarin (Coumadin) — Estrogens can affect clotting factors, which may change warfarin requirements. INR monitoring is recommended if you are on anticoagulation therapy.

Lamotrigine (Lamictal) — OCPs significantly reduce lamotrigine blood levels in some patients. This can lead to seizure breakthrough in patients with epilepsy. Conversely, stopping OCPs can cause lamotrigine levels to spike. This combination requires careful monitoring by your neurologist.

Supplements and Herbal Products

Don't overlook supplements and herbal products — some can interact with your birth control:

St. John's Wort (Hypericum perforatum) — This popular herbal supplement for depression is a known enzyme inducer. It can significantly reduce estrogen and progestin levels, potentially reducing contraceptive effectiveness. Avoid while taking Nortrel 1/35 21 Day.

What About Antibiotics?

For years, patients were told that common antibiotics (amoxicillin, doxycycline, etc.) could reduce birth control effectiveness. Current evidence does NOT support this for most antibiotics. The exception is rifampin (rifampicin), which is a strong enzyme inducer and does reduce OCP levels. Routine antibiotics for common infections (UTIs, ear infections, respiratory infections) do not reduce the effectiveness of Nortrel 1/35 21 Day, though backup contraception during illness-related vomiting and diarrhea is still important.

Always Tell Every Provider About Nortrel 1/35 21 Day

Any doctor or healthcare provider who prescribes you a new medication should know you are taking Nortrel 1/35 21 Day. This is especially important when seeing specialists (neurologists, infectious disease doctors, oncologists) who may not routinely ask about contraceptive use.

For more information about Nortrel 1/35 21 Day, see our guide on Nortrel 1/35 21 Day Side Effects. And if you need help finding your prescription in stock near you, visit medfinder.com.