Drug interaction between mycophenolate mofetil and tacrolimus detectable within therapeutic mycophenolic acid monitoring in renal transplant patients

The possible pharmacokinetic interaction between the new immunosuppressive mycophenolate mofetil (MMF) and tacrolimus (TAC), respectively, was assesse d by comparing routinely estimated mycophenolic acid (MPA) plasma trough le vels of 15 consecutive renal transplant patients receiving h MMF in combina tion with methylprednisolone (MEP) and cyclosporin A (CSA, 10 patients) or in combination with MEP and tacrolimus (TAC, 5 patients). Coadministration of TAC instead of CSA resulted in a significant increase of mean MPA plasma trough levels [3.4 +/- 1.3 mu g/mL (n = 22) versus 1.87 +/- 1.1 mu g/mL (n = 57); p < 0.001], despite lower MMF doses [1.5 +/- 0.5 g/d versus 1.7 +/- 0.3 g/d (not statistically significant)]. This elevation in MPA levels is possibly caused by an interaction between MMF and TAC and could lead to a r ecommendation to monitor MPA plasma levels with appropriate dose adjustment .