Tacrolimus Interactions

Pomelo contains furanocoumarins that inhibit intestinal CYP3A4 and P-glycoprotein, the two systems that limit tacrolimus absorption. A documented case in a renal transplant patient showed pomelo consumption nearly doubled tacrolimus blood levels, risking nephrotoxicity and neurotoxicity given tacrolimus's narrow therapeutic window.

CBD inhibits CYP3A4, CYP3A5, and P-glycoprotein, the main pathways that clear tacrolimus. A published case report documented an approximately 3-fold rise in dose-normalized tacrolimus levels after adding CBD, posing serious nephrotoxicity, neurotoxicity, and over-immunosuppression risk in transplant patients.

St. John's wort induces CYP3A4 and P-glycoprotein, slashing tacrolimus blood concentrations and risking acute graft rejection. Conversely, abrupt discontinuation of the herb can unmask tacrolimus nephrotoxicity as levels rebound.

Grapefruit furanocoumarins irreversibly inhibit intestinal CYP3A4, increasing tacrolimus AUC by roughly 28% and Cmax by up to 73%. Case reports describe trough levels tripling after grapefruit ingestion, producing nephrotoxicity and neurotoxicity.

Tacrolimus is a calcineurin-inhibitor immunosuppressant used after solid-organ transplant. Lactobacillus species have caused bacteremia, endocarditis, and liver abscess in transplant recipients on tacrolimus, including a published case of recurrent Lactobacillus rhamnosus bacteremia in a renal transplant patient.

Cranberry juice has been shown to inhibit intestinal CYP3A enzymes, and tacrolimus is heavily metabolized by intestinal CYP3A4 and CYP3A5. The expected direction is an increase in tacrolimus trough levels, raising the risk of nephrotoxicity and tremor, although published cases are scarce and one case unexpectedly reported a decrease.