Increased cyclosporine blood concentrations due to verapamil administration.

Cyclosporine is an immunosuppressive agent used to prevent rejection of transplanted organs. Monitoring cyclosporine blood concentrations is important to ensure adequate levels to prevent graft rejection while minimizing the risk of toxicity. A 45-year-old man who received a kidney transplant seven months previously is described. He had been receiving cyclosporine along with azathioprine and prednisone for immunosuppression since the transplant. His cyclosporine blood concentrations and renal function were stable during this time. Due to uncontrolled hypertension, sustained-release (SR) verapamil 240 mg/d was added with no change in cyclosporine levels. However, after increasing the dose of verapamil SR to 360 mg/d a dramatic increase in cyclosporine concentrations occurred. His renal function remained stable during this time. The interaction between cyclosporine and the calcium-channel blocking agents along with a possible nephroprotective effect of the calcium-channel blocking agents when used with cyclosporine are discussed.