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Many drugs can cause a myopathy.1–10 The pathophysiological mechanisms are diverse and, in many instances, unclear. Medications can have either a direct or an indirect adverse effect on muscle. The direct effect can be focal, as might occur secondary to a drug being injected into tissue, or more commonly generalized. Indirect toxic effects may result from the agent creating an electrolyte imbalance or inducing an immunological reaction. Muscle fibers may undergo necrosis as a result of the drug directly disrupting the sarcolemma, nuclear or mitochondria function, or that of other organelles. In this chapter, we classify the toxic myopathies according to their presumed pathogenic mechanisms (Table 35-1).
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