Drugs Causing Muscle Disease

Muscle weakness and/or myalgia is a common complaint among rheumatologic patients, and rheumatologists are aware of the importance of correctly diagnosing autoimmune myositis. However, while the differential diagnosis of muscle weakness should almost always also include drug effects, such effects may be difficult to identify. Many drugs can cause myopathies, and such myopathies may range widely from asymptomatic elevations in the serum creatine phosphokinase (CK) levels to severe myalgias, cramps, exercise intolerance, muscle weakness, and even rhabdomyolysis. Reviewing the literature frequently results in confusion because individual drugs may cause varying effects in different patients and imprecise terminologies are used to describe muscle pathology. In this article, some of the commonly used drugs that may induce myopathies, and the clinical syndromes, diagnosis, and management of these drug-induced myopathies are reviewed. For the convenience of the reader, the potential offending agents are segregated according to their major clinical indications.