ArticlesOxybutynin Does Not Affect Cyclosporin Blood LevelsSpringate, James E.Author Information Department of Pediatrics, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, New York Received August 14, 2000; accepted November 15, 2000. Address correspondence and reprint requests to James E. Springate, M.D., Division of Nephrology, The Children's Hospital, 219 Bryant St., Buffalo, NY 14222. Therapeutic Drug Monitoring: April 2001 - Volume 23 - Issue 2 - p 155-156 Buy Abstract Cyclosporin is an important immunosuppressive medication used to prevent organ rejection. Drug interactions that alter its blood levels can cause serious problems with toxicity or transplant rejection. Current evidence indicates that both cyclosporin and oxybutynin, which is used to treat bladder dysfunction, are metabolized by the cytochrome P450 3A enzyme system, raising the possibility of an adverse interaction between these medications. However, a study of two children receiving cyclosporin with and without oxybutynin revealed no significant changes in trough blood cyclosporin concentrations. © 2001 Lippincott Williams & Wilkins, Inc.