Effect of Erythromycin on Cyclosporine Levels

Abstract

To the Editor: The immunosuppressant cyclosporine is extensively metabolized in the liver by the cytochrome P-450 hepatic enzymes.¹ Drugs known to induce these enzymes and increase the clearance of cyclosporine include phenytoin, phenobarbital, and rifampin.^{2 3 4} Ketoconazole inhibits the function of these enzymes and has been shown to increase blood concentrations of cyclosporine.⁵ We report a case that suggests that erythromycin inhibits the clearance of cyclosporine.A 35-year-old woman with renal failure secondary to diabetes mellitus underwent cadaveric renal transplantation. Immunosuppression was achieved with oral cyclosporine (17 mg per kilogram of body weight per day) and steroids. Acute rejection on postoperative . . .