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

Estratest (esterified estrogens/methyltestosterone) contains two active hormones — an estrogen and a synthetic testosterone — which means its interaction profile includes interactions from both components. Some of these interactions are serious and require careful management. This guide covers the most important drug, food, and supplement interactions you need to know about.

Always tell every prescriber, specialist, urgent care provider, and pharmacist that you take Estratest/EEMT. Hormone combinations interact with a wide range of common medications.

Major Drug Interactions (Avoid or Use With Great Caution)

Warfarin (Coumadin) — MAJOR

Methyltestosterone significantly increases the anticoagulant effect of warfarin (Coumadin). Taking both can dramatically raise your INR (blood clotting time), leading to serious or life-threatening bleeding. If you are on warfarin and need to start Estratest (or vice versa), your anticoagulation must be closely monitored with frequent INR checks and likely warfarin dose reductions.

Cyclosporine — MAJOR

Methyltestosterone decreases the metabolism of cyclosporine (Sandimmune, Neoral), causing cyclosporine blood levels to rise. This can lead to serious nephrotoxicity (kidney damage) and hepatotoxicity (liver damage). The combination should be avoided if at all possible. If both must be used, cyclosporine levels require very close monitoring.

Aromatase Inhibitors — AVOID COMBINATION

Aromatase inhibitors (anastrozole/Arimidex, letrozole/Femara, exemestane/Aromasin) work by blocking estrogen production and are used in the treatment of hormone-receptor-positive breast cancer. Taking them together with Estratest is directly counterproductive — the estrogen from Estratest undermines the purpose of aromatase inhibitors. These drugs should not be taken together.

Moderate Drug Interactions (Use With Caution, Monitoring Required)

Imipramine (Tofranil)

Taking methyltestosterone with imipramine (a tricyclic antidepressant) has been reported to cause paranoia in some patients. Alert your prescriber if you are taking both.

Insulin and Oral Diabetes Medications

Androgens (like methyltestosterone) may enhance the hypoglycemic (blood sugar-lowering) effect of insulin and oral diabetes medications (sulfonylureas like glimepiride, glipizide, glyburide). Diabetic patients taking Estratest should monitor blood glucose more closely, especially when starting or stopping the hormone therapy.

CYP Enzyme Inducers (Drugs That Lower Hormone Levels)

Several drugs increase the activity of liver enzymes (CYP3A4) that metabolize estrogens, potentially reducing Estratest's effectiveness:

Carbamazepine (Tegretol): Anti-seizure medication

Phenobarbital: Anti-seizure medication

Rifampin (Rifadin): Antibiotic used for tuberculosis

If you take any of these, your prescriber may need to adjust your hormone dose or use an alternative hormone therapy formulation.

CYP Enzyme Inhibitors (Drugs That Raise Hormone Levels)

Conversely, drugs that inhibit CYP3A4 can increase estrogen blood levels, potentially increasing side effects and risks:

Ketoconazole (Nizoral): Antifungal

Itraconazole (Sporanox): Antifungal

Erythromycin / Clarithromycin: Antibiotics

Ritonavir (HIV protease inhibitor): Significant CYP inhibitor

Epoetin Alfa (Procrit, Epogen)

Androgens enhance the body's response to epoetin alfa, meaning a lower dose of the anemia medication may be needed. Your doctor should monitor your response to epoetin alfa if you're taking both.

Food Interactions

Grapefruit and Grapefruit Juice

Grapefruit contains compounds that inhibit CYP3A4, the main enzyme that metabolizes estrogens. Eating grapefruit or drinking grapefruit juice while taking Estratest may increase estrogen blood levels, potentially amplifying both benefits and side effects. Moderate intake is generally acceptable for most people, but excessive grapefruit consumption while on hormone therapy is not recommended.

Supplement and Herbal Interactions

St. John's Wort

St. John's Wort is a strong CYP3A4 inducer and can significantly reduce estrogen blood levels, potentially making your hormone therapy less effective. Avoid St. John's Wort while taking Estratest.

Herbal Menopause Supplements

Some herbal supplements marketed for menopause (such as black cohosh, red clover, or phytoestrogens) may have estrogenic activity and could add to the estrogen effects of Estratest in unpredictable ways. Always tell your doctor and pharmacist about all supplements you take.

How to Manage Drug Interactions

Maintain a complete medication list: Include all prescriptions, OTC drugs, vitamins, and supplements

Tell every new prescriber and pharmacist: Don't assume they'll see your full medication list — proactively mention Estratest/EEMT every time

Use one pharmacy: Filling all prescriptions at the same pharmacy allows the pharmacist's system to catch drug interactions automatically

Ask before adding new medications: Before starting any new prescription, OTC drug, or supplement, ask your pharmacist about potential interactions with Estratest

For a full overview of Estratest side effects, see our companion guide: Estratest Side Effects: What to Expect and When to Call Your Doctor.