Muscular fibrosis due to chronic intramuscular administration of narcotic analgesics

Chronic intramuscular injections, particularly of narcotic analgesics, are an uncommon cause of myopathy. We report two patients with pentazocine- and meperidine-related myopathy. Narcotic-induced muscular fibrosis and contractures must be considered in patients with a pattern of muscle involvement that does not conform to any recognized myopathy, but allows for self-administration of injections. Trauma due to needle puncture, repetitive infections and a local myotoxic effect of the drugs probably contribute to these lesions.