Polymyositis developing after prolonged injections of pentazocine.

Pentazocine is a frequently used analgesic drug. Numerous complications have been reported in association with its use, including skin fibrosis, skin ulceration, abnormal skin pigmentation and symmetrical myopathy. Fibrous myopathy is a rare but conspicuous complication of prolonged pentazocine injection. However, inflammatory myopathy has not previously been related to this substance abuse. We describe a patient who developed polymyositis after 13 months of pentazocine injections.