Why Drug Interactions Matter with Duavee

When you take more than one medication — or even certain supplements or foods — they can affect how each other works. Some interactions make a drug less effective. Others can increase side effects or create new risks.

Duavee (Conjugated Estrogens/Bazedoxifene) is processed by your liver, which means many common medications can speed up or slow down how your body handles it. Knowing these interactions ahead of time can help you and your doctor make safer treatment decisions.

This guide covers the major and moderate drug interactions with Duavee, plus supplements, foods, and drinks to watch out for.

How Drug Interactions Work with Duavee

Duavee's estrogen component is broken down in the liver by an enzyme system called CYP3A4. Anything that speeds up or slows down this enzyme can change how much estrogen is active in your body:

• CYP3A4 inducers speed up the enzyme → estrogen gets broken down faster → Duavee may not work as well
• CYP3A4 inhibitors slow down the enzyme → estrogen stays in your body longer → higher estrogen levels and potentially more side effects

This is why your doctor needs to know every medication and supplement you take before prescribing Duavee.

Medications That Interact with Duavee

Major Interactions

These interactions can significantly affect how Duavee works or increase your risk of serious side effects:

• Rifampin (Rifadin) — A powerful CYP3A4 inducer used to treat tuberculosis. Can dramatically reduce estrogen levels, making Duavee much less effective.
• Carbamazepine (Tegretol) — An anticonvulsant and mood stabilizer. Also a strong CYP3A4 inducer that can lower estrogen levels.
• Phenytoin (Dilantin) — Another anticonvulsant that induces CYP3A4 and can reduce Duavee's effectiveness.
• Ketoconazole (Nizoral) — An antifungal that strongly inhibits CYP3A4, potentially increasing estrogen levels and side effect risk.
• Ritonavir (Norvir) — An HIV protease inhibitor that is a potent CYP3A4 inhibitor. Can significantly increase estrogen exposure.
• Tamoxifen (Nolvadex) — Used for breast cancer treatment and prevention. Tamoxifen and bazedoxifene may potentially antagonize each other's effects since both act on estrogen receptors. Using them together is generally not recommended.

Moderate Interactions

• Erythromycin (E-Mycin, Ery-Tab) — An antibiotic that moderately inhibits CYP3A4, which may increase estrogen levels during treatment.
• Itraconazole (Sporanox) — An antifungal and moderate-to-strong CYP3A4 inhibitor.
• Warfarin (Coumadin) — Estrogens can affect blood clotting, which may alter how well Warfarin works. If you take Warfarin, your doctor will need to monitor your INR more closely when starting or stopping Duavee.
• Thyroid medications (Levothyroxine/Synthroid) — Estrogens increase thyroid-binding globulin in the blood, which can reduce the amount of active thyroid hormone available. Your thyroid dose may need adjustment when you start Duavee.
• Corticosteroids (Prednisone, Dexamethasone) — Estrogens may enhance the anti-inflammatory effects of corticosteroids, potentially changing how they work.
• Other estrogen or SERM products — Do not take Duavee with other estrogen-containing products (like estrogen patches, rings, or creams) or other SERMs (like Raloxifene). Using multiple products that affect estrogen receptors increases risk without additional benefit.

Supplements and OTC Products to Watch

It's not just prescription drugs you need to worry about. Several common supplements and over-the-counter products can interact with Duavee:

• St. John's Wort — This popular herbal supplement for mood is a strong CYP3A4 inducer. It can significantly reduce estrogen levels and make Duavee less effective. Avoid this combination.
• Black Cohosh — Sometimes used for menopause symptoms. While not a strong CYP3A4 interactor, combining it with hormone therapy like Duavee hasn't been well studied. Talk to your doctor before using both.
• Calcium and Vitamin D supplements — These are generally safe and even recommended alongside Duavee for osteoporosis prevention. No significant interaction.
• Melatonin — Estrogen may affect melatonin metabolism. While this isn't a dangerous interaction, mention it to your doctor if you use melatonin regularly.

Food and Drink Interactions

Grapefruit and Grapefruit Juice

Grapefruit is a well-known CYP3A4 inhibitor. Drinking grapefruit juice or eating grapefruit while taking Duavee can increase estrogen levels in your blood. While an occasional glass is unlikely to cause problems, regular consumption should be discussed with your doctor.

Alcohol

Alcohol isn't a direct drug interaction with Duavee, but it's worth mentioning. Alcohol can worsen some of Duavee's side effects like dizziness and nausea. It also affects liver function, which is where Duavee is processed. Moderate alcohol consumption is generally okay, but heavy drinking should be avoided.

St. John's Wort Tea

If you drink herbal teas containing St. John's Wort, the same CYP3A4 interaction applies. Check your tea ingredients if you're a regular herbal tea drinker.

What to Tell Your Doctor

Before starting Duavee, give your doctor a complete picture of everything you take:

• All prescription medications — including any you take irregularly or "as needed"
• Over-the-counter medications — pain relievers, antacids, allergy medications, sleep aids
• Herbal supplements — St. John's Wort, black cohosh, evening primrose oil, and others
• Vitamins and minerals — including calcium, vitamin D, and multivitamins
• Recreational substances — including cannabis products, which may also affect liver enzymes

Questions to Ask

• Do any of my current medications interact with Duavee?
• Will I need dose adjustments for any other medications when starting Duavee?
• Are there specific supplements I should stop or start?
• Should I avoid grapefruit?

Your pharmacist is also an excellent resource for checking drug interactions. When you fill your Duavee prescription, ask the pharmacist to run an interaction check against your full medication list.

Final Thoughts

Drug interactions with Duavee are manageable — but only if your healthcare team knows everything you're taking. The biggest risks come from CYP3A4 inducers (like Rifampin and St. John's Wort) that can make Duavee less effective, and CYP3A4 inhibitors (like Ketoconazole) that can increase estrogen levels beyond what's intended.

Always keep your medication list up to date, and don't hesitate to ask questions. For more about Duavee, check out our guides on side effects, uses and dosage, and how it works.

Having trouble finding Duavee at your pharmacy? Medfinder can help you locate it in stock near you.