Co-administration of ketoconazole and tacrolimus to kidney transplant recipients: cost minimization and potential metabolic benefits.

To evaluate the effects of the co-administration of tacrolimus and ketoconazole to a group of kidney transplant recipients, we studied 30 kidney transplant recipients with stable kidney function who were maintained on tacrolimus-based immunosuppression. They were prescribed ketoconazole (100 mg/day) with a concomitant reduction in daily tacrolimus dose to maintain its level within the therapeutic range. The study included 19 males and 11 females with a mean age of 36 ± 12 years. All patients were at least three months post-transplant and had tacrolimus trough levels within the therapeutic range of 5-7 ng/mL. Desired tacrolimus trough levels could be achieved in 29/30 patients after the addition of ketoconazole. This resulted in a significant reduction of the median tacrolimus dose from 5 mg/day (range 3-20 mg/day) at baseline to 2 mg/day (range 1-4 mg/day) (P = 0.00). The median reduction in the tacrolimus dose was 63% (range 50-83%). The median monthly tacrolimus cost dropped from 375 US$ per patient (range 225-1440 US$) to 150 US$ per patient (range 120-300 US$). There were no reported adverse drug effects during the study period. After one year of follow-up, there was a small but significant improvement in the estimated glomerular filtration rate (72 ± 18 versus 78 ± 20 mL/min, P = 0.01) and a significant reduction in serum uric acid levels (7.7 ± 1.7 versus 5.9 ± 0.8 mg/dL, P = 0.003). The co-administration of ketoconazole and tacrolimus to kidney trans-plant recipients is safe and significantly reduces the cost of immunosuppression. In addition, this combination appears to have a beneficial effect on kidney function.