LONG-LASTING MUSCLE-RELAXANT ACTIVITY OF EPERISONE HYDROCHLORIDE AFTER PERCUTANEOUS ADMINISTRATION IN RATS

Potency and duration of muscle relaxant activity of eperisone hydrochl oride were examined after percutaneous administration in the intercoll icular decerebrated rat rigidity model and compared to those of eperis one after intravenous injection. A continuous movement was loaded on t he hindlimb of the rat model to maintain stable rigidity. The tonus of the hindlimb was recorded by EMG from the triceps surae and was quant ified by using the public domain NIH Image program. Eperisone ointment administered percutaneously showed significant muscle relaxant activi ty at 8.4 cm(2) (4.2 mg of eperisone)/rat. The effect was dose-depende nt and lasted over 60 min. Intravenously injected eperisone showed sig nificant activity at 1.25 mg/kg, but the decrease of tone was lost wit hin 30 min after injection. Plasma eperisone levels were monitored in the same model, and they were well correlated to the dosage. These res ults suggest that percutaneously administered eperisone is absorbed ef ficiently and shows potent and long-lasting muscle relaxant activity.