Serum creatine phosphokinase concentrations after intramuscular chlordiazepoxide and its solvent

Serum creatine phosphokinase (CPK) concentrations were determined in healthy volunteers for the first 48 hours after intramuscular injection of 50 mg chlordiazepoxide hydrochloride or of its solvent alone. Intramuscular injection of both the drug solution and its solvent was painful and caused CPK elevations. The CPK rise due to the drug solution was 33 per cent higher than that due to the solvent alone, but the difference was not significant. The pH of the solvent preparation is low and it contains high concentrations of propylene glycol. The pain and muscle damage due to injection of the solvent could be due to its acidity and its high osmolarity. Problems associated with intramuscular injections of water-insoluble drugs are not resolved by the use of such solvent preparations.