Drug Interactions with Estradiol/Norethindrone/Relugolix

If you're taking Myfembree — the brand name for Estradiol/Norethindrone/Relugolix — it's important to know which other medications, supplements, and even foods can interact with it. Some interactions can make Myfembree less effective, while others can increase the levels of the drug in your body and raise the risk of side effects.

This guide covers the major and moderate interactions, what to avoid, and what to tell your doctor before starting treatment.

How Drug Interactions Work with Myfembree

Myfembree contains three active ingredients, each with its own potential for interactions:

• Relugolix is transported into your bloodstream through a protein called P-glycoprotein (P-gp). Medications that affect this transporter can dramatically change how much Relugolix your body absorbs.
• Estradiol and Norethindrone Acetate are processed primarily through the CYP3A4 enzyme in your liver. Drugs that speed up or slow down this enzyme can alter hormone levels.

Because Myfembree is a fixed-dose combination — you can't adjust the dose of one ingredient without changing all three — interactions are especially important to manage.

Major Drug Interactions

These interactions are the most clinically significant and typically require avoiding the combination entirely or taking specific precautions.

P-glycoprotein (P-gp) Inhibitors

P-gp inhibitors can significantly increase Relugolix blood levels, raising the risk of side effects. Avoid taking these medications with Myfembree, or if unavoidable, take Myfembree first and wait at least 6 hours before taking the P-gp inhibitor:

• Cyclosporine (Neoral, Sandimmune) — an immunosuppressant
• Erythromycin — an antibiotic
• Ketoconazole (Nizoral) — an antifungal
• Verapamil (Calan, Verelan) — a blood pressure/heart medication

If your doctor determines that one of these medications is essential, the 6-hour separation can help reduce the interaction, but close monitoring is necessary.

Strong CYP3A4 Inducers

These medications speed up the breakdown of Myfembree's components in your liver, potentially making the medication less effective:

• Rifampin (Rifadin) — an antibiotic used for tuberculosis
• Carbamazepine (Tegretol) — an anticonvulsant/mood stabilizer
• Phenytoin (Dilantin) — an anticonvulsant
• St. John's Wort — an herbal supplement (more on this below)

If you need one of these medications, your doctor may need to consider alternative treatments for your fibroids or endometriosis, or alternative medications for the other condition.

Combined Hormonal Contraceptives

This is a critical one: you cannot take combined hormonal contraceptives while on Myfembree. This includes:

• Combined birth control pills (containing estrogen and progestin)
• Hormonal patches (e.g., Xulane)
• Vaginal rings (e.g., NuvaRing)

These add more estrogen and progestin on top of what's already in Myfembree, which interferes with the medication's ability to suppress your hormonal axis and increases the risk of blood clots. Use non-hormonal contraception instead — such as condoms, a copper IUD (Paragard), or a diaphragm.

Moderate Drug Interactions

These interactions may require monitoring or dose adjustments for the other medication:

• CYP3A4 inhibitors — Medications that slow down the CYP3A4 enzyme (such as certain antifungals, protease inhibitors, or grapefruit juice) may increase Norethindrone levels in your blood. While this isn't usually dangerous, it may increase side effects from the progestin component.
• Anticonvulsants that induce CYP3A4 — Beyond the strong inducers listed above, other anticonvulsants like Oxcarbazepine (Trileptal) or Topiramate (Topamax, at higher doses) may also reduce Myfembree's effectiveness to some degree.
• Thyroid replacement medications — If you take Levothyroxine (Synthroid) or other thyroid hormones, be aware that the estrogen in Myfembree can increase thyroid-binding globulin (TBG). This may require your doctor to increase your thyroid medication dose and monitor your thyroid function more frequently during treatment.
• Protease inhibitors — Certain HIV medications like Fosamprenavir (Lexiva) may interact with Norethindrone Acetate. If you're on HIV treatment, discuss all your medications with both your OB/GYN and your infectious disease specialist.

Supplements and Over-the-Counter Products to Watch

St. John's Wort

This is the most important supplement to avoid. St. John's Wort is a potent CYP3A4 inducer that can significantly reduce the effectiveness of all three components of Myfembree. Even though it's sold over the counter as a natural mood enhancer, it interacts with Myfembree the same way a prescription drug would. Do not take St. John's Wort while on Myfembree.

Other Supplements to Discuss

• Black cohosh — Sometimes used for menopausal symptoms. While not a known direct interaction, it has estrogenic effects that could theoretically interfere with treatment. Discuss with your doctor.
• Calcium and Vitamin D — These are actually recommended during Myfembree treatment to help support bone health, especially since the medication can affect bone mineral density. Ask your doctor about appropriate doses.
• Iron supplements — If you've been anemic from heavy fibroid bleeding, your doctor may recommend iron supplementation. This doesn't interact with Myfembree and is generally safe to take concurrently.

Food and Drink Interactions

• Food — Myfembree can be taken with or without food. There are no specific food restrictions.
• Grapefruit and grapefruit juice — Grapefruit is a known CYP3A4 inhibitor that could theoretically increase Norethindrone levels. While this hasn't been specifically studied with Myfembree, it's reasonable to avoid consuming large amounts of grapefruit regularly during treatment. An occasional glass is unlikely to cause problems, but daily consumption may be worth discussing with your pharmacist.
• Alcohol — There's no direct interaction between alcohol and Myfembree. However, since both can affect liver function, moderate alcohol consumption is advisable. If you have any liver concerns, discuss this with your doctor.

What to Tell Your Doctor

Before starting Estradiol/Norethindrone/Relugolix, give your doctor a complete list of everything you take, including:

• All prescription medications — especially antibiotics, antifungals, blood pressure medications, anticonvulsants, immunosuppressants, and HIV medications
• Over-the-counter medications — including pain relievers, antacids, and allergy medications
• Herbal supplements — especially St. John's Wort, black cohosh, and any other herbal products
• Vitamins and minerals — your doctor may want to add calcium and vitamin D if you're not already taking them
• Hormonal products — including birth control, hormone replacement therapy, or any other hormonal medications

Also tell your doctor if you:

• Have a history of blood clots, stroke, or heart disease
• Have liver problems
• Have been diagnosed with osteoporosis or have risk factors for bone loss
• Are taking thyroid medication (dose may need adjustment)

Your pharmacist is another excellent resource. Every time you fill a new prescription or start a new supplement, ask your pharmacist to check for interactions with Myfembree.

Final Thoughts

Drug interactions with Estradiol/Norethindrone/Relugolix are manageable when you and your healthcare team are aware of them. The most critical ones to remember: avoid P-gp inhibitors (or separate by 6 hours), stay away from strong CYP3A4 inducers like Rifampin and St. John's Wort, and never combine Myfembree with hormonal contraceptives.

Keeping an updated medication list and communicating openly with your doctor and pharmacist are the best ways to prevent problems. For more information on this medication, see our guides on what Estradiol/Norethindrone/Relugolix is and its side effects.

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