Increased systemic exposure of once daily tacrolimus in renal transplant recipients on marine omega-3 fatty acid supplementation.

High daily doses of marine omega-3 fatty acids (FAs) from fish and seafood may have beneficial cardiovascular effects in renal transplant recipients (RTRs) (1, 2). A recent randomized clinical trial demonstrated that daily supplementation with high-dose marine omega-3 FAs lowered plasma triglyceride and C-reactive protein levels (1). In some parts of the world, high intake of marine omega-3 FAs is recommended for the general population and it is likely that RTRs use omega-3 FA supplements without consulting a transplant physician (2). Previous reports indicate increased systemic exposures of cyclosporine and sirolimus in patients receiving high-dose marine omega-3 FA supplements (3, 4) which could be related to reduced drug metabolism supported by the in vitro experimental observation of an inhibitory effect of omega-3 FAs on cytochrome P450 (CYP) 3A enzymes (5) expressed in the intestine and liver. The present study aimed to examine the effect of marine omega-3 FAs on the pharmacokinetics of tacrolimus.