Is cyclosporine toxic to the heart?

Cardiotoxicity caused by cyclosporine was studied in experimental rats by the uptake of radiopharmaceuticals (technetium 99m-labeled pyrophosphate and indium 111-labeled antimyosin) and histologic examination of heart tissues. A dose of 50 mg/kg (body weight) of cyclosporine and an equal volume of vehicle (cremophor-EL) were injected into the rats subcutaneously for 7 or 11 consecutive days. A statistically significant difference (p < 0.05) was noted between the uptake of the radiopharmaceuticals in the hearts of cyclosporine-treated rats compared to the control rats. For 99mTc pyrophosphate, the cardiac uptake ratios of cyclosporine-treated rats to control rats were 2.13 and 4.08 for 7-day and 11-day treatment periods, respectively. For 111In antimyosin, the ratios were greater than 2 for both 7-day and 11-day treatment periods. Histologically, vacuoles were found in single or focal groups of myocytes with interstitial edema in the hearts of cyclosporine-treated rats compared to the control rats. The results of both the uptake of the radiopharmaceuticals and the histologic evidence indicate cell injury in the hearts of cyclosporine-treated rats. Cyclosporine therefore seems to be toxic to the heart tissue.