Effects of Cyclosporine in Lowering Red Blood Cell Technetium-99m Labeling Efficiency

Abstract

Cyclosporine, an immunosuppressant drug taken by many transplant patients, has been found to significantly lower red blood cell (RBC) labeling efficiency to an unacceptable level (below 50%.) We have observed an intermittent RBC ^99mTc labeling problem in our cardiac transplant patients. After closely examining our in vitro labeling technique and finding no obvious errors, we began to check for a chemical interference from patient medications. We reviewed a detailed list of all medications these transplant patients were taking and felt the immunosuppressant drugs, cyclosporine and Immuran, to be the most suspect. We have currently studied 10 cardiac transplant patients who were undergoing radionuclide ventriculogram (RVG) examinations at our institution. We discovered that peak concentrations of cyclosporine in whole blood of greater than 100 ng/ml significantly decreased RBC labeling efficiency. We found no labeling interference from the other medications, including Immuran.