Amiodarone and desethylamiodarone toxicity in isolated hepatocytes in culture

Amiodarone, a class III antiarrhythmic drug, has been found to be effective in the management of patients with life-threatening ventricular arrhythmias. Recent reports describe the presence of myelinoid inclusion bodies following amiodarone therapy in liver, myocardium, white blood cells, lung, cornea, skin, and lymph nodes; their relationship to toxicity is unclear. The exact role of desethylamiodarone, the major metabolite, of amiodarone in systemic toxicity of the parent drug is not known. Concentration-response relationships for amiodarone and desethylamiodarone were investigated by adding 1-50 micrograms/ml of the compounds of dimethyl sulfoxide (controls) to hepatocytes isolated from Sprague-Dawley rats and cultured in Leibovitz L-15 medium. Using lactate dehydrogenase release into the medium to quantitate cell death, both drugs were found to cause cell death in a concentration-dependent manner within 24 hr of incubation; this data showed desethylamiodarone to be significantly more toxic than amiodarone. In experiments with 50-micrograms/ml concentrations of amiodarone or desethylamiodarone, we found desethylamiodarone to produce a significantly greater release of lactate dehydrogenase as compared with amiodarone within 2-4 hr. Electron microscopic studies indicated the presence of myelinoid inclusion bodies at early culture stages followed by progressive swelling of mitochondria and rough endoplasmic reticula, disruption of membranes, aggregation of subcellular structures, and ultimately cell death. Ultrastructural changes occurred sooner in the hepatocytes treated with desethylamiodarone than with amiodarone. These data demonstrate that (i) desethylamiodarone is more toxic than amiodarone; (ii) acute toxicity of desethylamiodarone and amiodarone can be quantitated by lactate dehydrogenase release; (iii) both desethylamiodarone and amiodarone can induce myelinoid inclusion bodies in cultured hepatocytes; and (iv) toxicity is characterized by progressive subcellular changes leading to cell death.