[Intramuscular injections and activity of serum creatine phosphokinase. Histopathological study in animal experiments].

In healthy Labrador dogs a single intramuscular injection of benzoctamin, diazepam and pethidin leads to a distinct increase in serum-creatine-phosphokinase (SCK) activity, whilst a single intramuscular injection of physiologic saline has no effect whatsoever. Intravenous injection of an identical dose of the above-mentioned drugs leaves SCK activity unchanged. Muscle specimens of the injection site, excised 5 days after intramuscular injection of the same drugs, display muscle cell necrosis, macrophage proliferation and reparative changes. The impressive histological alterations point to the striated muscle cell as a probable source of the increase in SCK activity (MM fraction).