Focal myopathy associated with chronic intramuscular injection of piritramide.

We report a patient in whom chronic intramuscular piritramide led to a focal fibrotic myopathy. Since piritramide myotoxicity has never been reported, we have studied its effect on rat skeletal muscle. Chronic intramuscular piritramide led to fibrous connective tissue replacement of rat skeletal muscle, similar to that found in the patient's muscle. Although the pathogenetic mechanism of piritramide myopathy is unclear, we caution against prolonged intramuscular use of piritramide to prevent this potentially debilitating adverse effect.