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

Sirolimus (brand name Rapamune) has some of the most clinically significant drug interactions of any medication in transplant medicine. Because sirolimus has a narrow therapeutic range — the gap between "too little" (rejection risk) and "too much" (toxicity) is narrow — even modest changes to blood levels caused by another drug or food can have serious consequences.

This guide covers the most important sirolimus interactions so you can have an informed conversation with your transplant team and every other doctor or pharmacist you see.

Why Sirolimus Has So Many Interactions

Sirolimus is primarily metabolized by the liver enzyme CYP3A4 and also transported by P-glycoprotein (P-gp). Any drug that inhibits or induces these systems will increase or decrease sirolimus blood levels, potentially pushing them out of the therapeutic range. Additionally, sirolimus amplifies the effects of other immunosuppressants and can interact pharmacodynamically (in terms of effect) even when blood levels don't change.

Contraindicated Drug Combinations (Never Use Together)

• Voriconazole (Vfend): This antifungal is a potent CYP3A4 inhibitor and dramatically increases sirolimus levels — potentially by 10-fold or more. The combination is contraindicated. If antifungal therapy is needed in a sirolimus patient, an alternative antifungal must be chosen.
• Mifepristone: Significantly increases sirolimus exposure through CYP3A4 inhibition. Contraindicated.

Major Drug Interactions (Avoid or Use With Extreme Caution)

The following drugs can significantly raise sirolimus blood levels (increasing toxicity risk):

• Ketoconazole, itraconazole, fluconazole: Antifungal medications that inhibit CYP3A4. Ketoconazole is one of the most potent inhibitors. Avoid if possible; if use is necessary, reduce sirolimus dose significantly and increase monitoring.
• Cyclosporine: Increases sirolimus AUC approximately 2-fold through CYP3A4 and P-gp inhibition. When used together, sirolimus must be taken 4 hours after cyclosporine and doses are carefully managed.
• Diltiazem, verapamil: These calcium channel blockers used for heart conditions also inhibit CYP3A4 and can raise sirolimus levels. Monitoring and possible dose adjustment are needed.
• Erythromycin, clarithromycin: Macrolide antibiotics that inhibit CYP3A4. Use azithromycin as an alternative when possible (less CYP interaction).
• HIV protease inhibitors (ritonavir, indinavir, etc.): Potent CYP3A4 inhibitors used to treat HIV. Can dramatically increase sirolimus levels — close monitoring required.

The following drugs can significantly lower sirolimus blood levels (increasing rejection risk):

• Rifampin (rifampicin): A potent CYP3A4 inducer used to treat tuberculosis. Can reduce sirolimus levels by up to 90%. Avoid if possible in transplant patients.
• Carbamazepine (Tegretol), phenytoin (Dilantin), phenobarbital: Anti-seizure medications that are strong CYP3A4 inducers. Discuss with your transplant team before starting or stopping any of these.
• Rifapentine: Another rifamycin antibiotic with strong CYP3A4 induction; avoid in sirolimus patients.

Food Interactions

• Grapefruit and grapefruit juice: AVOID. Grapefruit contains furanocoumarins that irreversibly inhibit CYP3A4 in the intestinal wall, significantly raising sirolimus levels. Even small amounts can have clinically significant effects.
• Food in general: Food significantly affects sirolimus absorption. Always take sirolimus the same way — either always with food or always without food — to maintain consistent blood levels.

Herbal and Supplement Interactions

• St. John's Wort (Hypericum perforatum): A popular herbal supplement for depression. It's a potent CYP3A4 inducer and will significantly reduce sirolimus levels. Absolutely avoid while taking sirolimus.
• Cannabidiol (CBD): CBD can inhibit CYP3A4 and may increase sirolimus levels. If you use CBD products, inform your transplant team — dose reduction and additional monitoring may be needed.
• Echinacea: May stimulate immune function and counteract sirolimus's immunosuppressive effects. Avoid while on immunosuppressants.

Vaccine Interactions

Live vaccines are contraindicated while taking sirolimus due to the risk that a weakened immune system could fail to contain the attenuated vaccine virus, causing active infection. Examples of live vaccines to avoid:

• MMR (measles, mumps, rubella)
• Varicella (chickenpox) / Zoster (shingles — live form only)
• Yellow fever
• Intranasal influenza vaccine (the live nasal spray flu vaccine — inactivated injectable flu shots are OK)

Non-live vaccines are generally safe to receive on sirolimus, though immune response may be diminished. Discuss your vaccination schedule with your transplant team.

Pharmacodynamic Interactions (Effect-Based)

Some medications don't change sirolimus blood levels but interact through their effects:

• Other immunosuppressants (tacrolimus, mycophenolate, corticosteroids): Used in combination with sirolimus in transplant regimens. Combined immunosuppression amplifies both infection risk and cancer risk — managed through careful monitoring.
• Adalimumab, anakinra, and other biologics: These immunomodulatory drugs further increase infection risk when combined with sirolimus.

What to Tell Every Doctor and Dentist

Because the interaction risk is so significant, always inform every healthcare provider — including dentists, urgent care physicians, and dermatologists — that you are taking sirolimus before any medication is prescribed. Carry your medication list with you at all times.

Key points to communicate:

• "I take sirolimus (Rapamune) for kidney transplant / LAM"
• "It is processed by the CYP3A4 enzyme, so I cannot take drugs that strongly inhibit or induce this enzyme without checking with my transplant team"
• "I cannot receive live vaccines"
• "Please contact my transplant team at [number] if you are uncertain"

For more information on sirolimus safety, see our companion article on

sirolimus side effects and when to call your doctor

And if you need help locating sirolimus at a pharmacy near you, medfinder is here to help.