Experimental heroin-induced myopathy: ultrastructural observations.

Electron microscopic analysis was used to study the ultrastructural changes taking place in rat soleus muscle following intraperitoneal administration of pure heroin. Degenerative changes observed consisted primarily of hypercontracted fibers at different stages of development. Evidence of regeneration was also found. Results show the myotoxic effect of pure heroin on skeletal muscle. The pathogenesis of muscle damage is discussed.