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

When you're being treated with Padcev (enfortumab vedotin-ejfv), the other medications, supplements, and foods you consume can affect how well Padcev works — or increase your risk of dangerous side effects. This is because the active drug payload in Padcev (MMAE) is primarily broken down by an enzyme system in the liver called CYP3A4.

Understanding Padcev's drug interactions is important for your safety. Always give your oncologist a complete list of every medication, supplement, vitamin, and herbal product you take before starting Padcev.

Why CYP3A4 Matters for Padcev Interactions

MMAE (monomethyl auristatin E) — the cytotoxic component of Padcev — is primarily metabolized by the CYP3A4 enzyme system in the liver. Many common medications either inhibit (block) or induce (speed up) this enzyme. When CYP3A4 is blocked, MMAE levels in your body can increase, raising your risk of toxicity. When CYP3A4 is induced, MMAE may be broken down too quickly, potentially making Padcev less effective.

Strong CYP3A4 Inhibitors: Drugs to Avoid While on Padcev

The following medications strongly inhibit CYP3A4 and should be avoided or used with extreme caution during Padcev treatment:

Antifungals: Ketoconazole, itraconazole, voriconazole, posaconazole

Antibiotics: Clarithromycin, telithromycin, erythromycin

HIV protease inhibitors: Atazanavir, ritonavir, lopinavir, indinavir

Other strong CYP3A4 inhibitors: Fexinidazole, etrasimod

If you need treatment with any of these drugs during Padcev therapy, contact your oncologist immediately. A dose adjustment or temporary treatment hold may be needed.

Strong CYP3A4 Inducers: Drugs That May Reduce Padcev's Effectiveness

Drugs that strongly induce CYP3A4 can accelerate MMAE breakdown, potentially reducing Padcev's anticancer effect. Use with caution and monitor clinical response:

Prostate cancer drugs: Apalutamide (Erleada), enzalutamide (Xtandi)

Antibiotics/antiparasitics: Rifampin (rifampicin)

Anti-seizure medications: Carbamazepine (Tegretol), phenytoin (Dilantin), phenobarbital

Food Interactions: Grapefruit and Grapefruit Juice

Grapefruit and grapefruit juice are potent CYP3A4 inhibitors. While Padcev is given by IV infusion (not orally), grapefruit compounds are absorbed from the GI tract and can still inhibit CYP3A4 metabolism of MMAE that circulates in the bloodstream after infusion.

Your oncology team may advise you to avoid grapefruit and grapefruit juice during Padcev treatment. Other citrus fruits (oranges, lemons, limes) do not have this interaction.

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Immunosuppressive Drug Interactions

Etrasimod (Velsipity), used for ulcerative colitis, can have additive immunosuppressive effects when combined with Padcev. This combination should be avoided or used with extreme caution due to increased infection risk.

Alcohol and Padcev: What Is Known?

There are no formal studies on alcohol's effect on Padcev's pharmacokinetics. However, alcohol can increase liver stress and compromise immune function, which is already challenged by cancer treatment. Patients are generally advised to minimize or eliminate alcohol consumption during Padcev therapy.

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Supplements and Herbal Interactions to Watch

Several herbal supplements can significantly affect CYP3A4 activity:

St. John's Wort: A potent CYP3A4 inducer — avoid completely during Padcev treatment

Milk thistle (silymarin): Some evidence of CYP3A4 modulation — discuss with your oncologist

Curcumin/turmeric supplements: May modulate CYP enzymes — disclose to your oncology team

Never take any new supplement or herbal product without first checking with your oncologist. Many herbal supplements are not regulated and can affect how cancer drugs work.

Hepatic Impairment: Another Drug Interaction Consideration

Padcev should not be used in patients with moderate or severe hepatic impairment (Child-Pugh B or C). Liver disease affects CYP3A4 metabolism of MMAE, increasing toxicity risk. If you are taking other medications that are known to be hepatotoxic (liver-toxic), your care team will monitor your liver enzymes (AST, ALT) closely.

What to Tell Your Doctor Before Starting Padcev

At your pre-treatment appointment, bring a complete medication list including:

All prescription medications, including any new prescriptions from other doctors

Over-the-counter drugs (including antacids, pain relievers, cold medicines)

All vitamins, minerals, and dietary supplements

Herbal products and teas

Any history of grapefruit or grapefruit juice consumption

Also read: Padcev Side Effects: What to Expect and When to Call Your Doctor.

If you need help locating a Padcev infusion center near you, visit medfinder.com.