Evaluation of renal function in transplant patients on tacrolimus therapy

Glomerular filtration rate (GFR), as measured by 24-hour creatinine clearance and clearance of iothalamate, and effective renal plasma flow, (ERPF), as measured by the clearance of para-aminohippuric acid (PAH), were evaluated at 2 weeks, 1 month, and 3 months after transplantation in 8 renal transplant patients and at 1 month and 1 year after transplantation in 9 liver transplant patients receiving tacrolimus (Prograf(R)) therapy. In renal transplant patients, there was a significant increase in GFR after transplantation. There was no change in GFR at 1 and 3 months as compared to 2 weeks after transplantation, while ERPF (ml/min/1.73 m(2)) was lower (p < 0.05) at 3 months (212 +/- 42) compared to 1 month (306 +/- 118) after transplantation. In liver transplant patients, GFR and ERPF were below normal despite normal serum creatinine concentrations, but there was no difference in GFR or ERPF at 1 month and 1 year after transplantation. Although below normal, renal function was well preserved in transplant patients;while receiving chronic tacrolimus therapy over the study period. Dosage alterations of renally eliminated drugs may be required for drugs with a narrow therapeutic index. (C) 2002 the American College of Clinical Pharmacology.