Emetine myopathy

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Abstract
SUMMARYThe effects of emetine on rat soleus (a red muscle) and the medial head of gastrocnemius (a relatively white muscle) were investigated. The drug was administered at a dosage of 1.25 mg. per kilogram daily for five, ten, or fifteen days. Throughout treatment, soleus was more severely affected than gastrocnemius. Loss of cross striations from small areas of soleus was noted by the fifth day. By the fifteenth day, 20 to 90% (average, 48%) of soleus fibers in a given plane showed multiple lesions, some as wide as the fibers and up to 250, μ long, but less than 10% of gastrocnemius fibers displayed occasional lesions by the fifteenth day. Two to 4% of fibers in 12 of 19 control soleus biopsies and 1% of fibers in 2 of 19 control gastrocnemius biopsies also contained small lesions of the same type. Enlarged and vesicular nuclei appeared in treated muscle fibers in increasing numbers from the fifth day on. Necrotic fibers, some undergoing phagocytosis, and slender regenerating fibers were found in treated muscles by the fifteenth day. Longitudinally oriented hydroxyadipaldehyde-fixed specimens of soleus muscle demonstrated decreases of mitochondrial oxidative enzyme activity in multiple, circumscribed regions. These areas increased in size and number over the course of the study and some, but not all, areas also displayed loss of cross striations within their confines. Loss of cross striations was found only in regions of decreased mitochondrial enzyme activity. Under the conditions of the experiment, emetine induced pathological alterations in muscle without recognizable morphological or physiological alterations in the neural components of the motor unit.

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