Tacrolimus Interactions

CBD inhibits CYP3A4, CYP3A5, and P-glycoprotein, the main pathways that clear tacrolimus. Case reports and a controlled pharmacokinetic trial show that adding CBD raises tacrolimus blood levels substantially, risking nephrotoxicity, neurotoxicity, and over-immunosuppression in transplant recipients, while stopping CBD abruptly can let levels crash and risk rejection.

St. John's wort induces the CYP3A4 enzyme and the P-glycoprotein transporter, which speeds up clearance of tacrolimus and lowers its blood levels, raising the risk of transplant rejection. Stopping the herb after the body has adjusted can let tacrolimus levels rebound, which has been linked to kidney toxicity.

Grapefruit furanocoumarins irreversibly inhibit intestinal CYP3A4, the enzyme that limits how much tacrolimus reaches the bloodstream. This can raise tacrolimus blood levels enough to cause kidney and nervous-system toxicity. Because the enzyme inhibition lasts for days, separating dose timing does not prevent it.

Pomelo contains furanocoumarins that inhibit intestinal CYP3A4 and P-glycoprotein, the systems that limit how much tacrolimus is absorbed. A documented case in a renal transplant patient showed pomelo consumption raised tacrolimus blood levels, and tacrolimus has a narrow therapeutic window where small swings can cause kidney or nervous-system toxicity, or under-immunosuppression and rejection.

Tacrolimus is a calcineurin-inhibitor immunosuppressant used after solid-organ transplant. In immunosuppressed transplant recipients, Lactobacillus probiotic organisms can cross the gut wall and cause bloodstream infection. Published case reports document Lactobacillus rhamnosus bacteremia in renal transplant patients on tacrolimus, and many probiotic strains are intrinsically vancomycin-resistant, making treatment harder.

The only human report on cranberry and tacrolimus showed tacrolimus levels falling sharply, not rising; lab studies predict the opposite, so the true direction is genuinely unpredictable. Because tacrolimus has a very narrow therapeutic window, any change in cranberry intake deserves a trough check.