Vitamin E reduces accumulation of amiodarone and desethylamiodarone and inhibits phospholipidosis in cultured human cells.

Chronic administration of amiodarone (AMIO), widely used by clinicians for the treatment of therapy-resistant cardiac arrhythmias, is frequently associated with serious side-effects. AMIO and its main metabolite desethylamiodarone (DEA) are known to induce phospholipidosis in vivo and in cultured cells presumably by inhibition of lysosomal phospholipid degradation. D-alpha-Tocopherol = vitamin E (alpha-TOC) was able to reduce AMIO and DEA toxicity in cell cultures. Results from the present study showed that alpha-TOC reduced phospholipidosis in cultured human skin fibroblasts chronically exposed to micromolar concentrations of AMIO and DEA and inhibited cumulative uptake of the drugs in a dose-dependent manner. A linear correlation was observed between cellular AMIO levels and phospholipid accumulation suggesting a stoichiometric relationship. alpha-TOC was also effective in clearing previously accumulated phospholipids after discontinuation of the drug treatment. The results can best be explained by an interference of alpha-TOC (a) with drug-phospholipid complex formation responsible for both phospholipid storage and drug accumulation, and (b) with pre-existing drug-phospholipid complexes, accelerating their dissociation and rendering phospholipids to substrates for lysosomal phospholipases. The finding raises hope that side-effects of AMIO and DEA can be prevented or made reversible by the administration of alpha-TOC. It must, however, be proven that the antiarrhythmic drug will still be effective.