薬理と治療

Abstract

The onset of the analgesic effect of plaster containing loxoprofen sodium（LOX）wasexamined electrophysiologically using a rat model of muscle pain. To establish an animalmodel of persistent mechanical hyperalgesia, saline at pH 4.0 was injected twice every 5 daysinto the gastrocnemius muscle. To quantify hyperalgesia, the paw withdrawal threshold tomechanical stimuli was measured. A total of 19 rats were selected on the basis of behavioralresults that showed mechanical hyperalgesia and were divided into the following two groups：LOX group（application of plaster containing LOX）and Base group（application of plaster withoutLOX）. Under halothane anesthesia（1 ％ in air）, an electromyogram（EMG）was recordedfrom the tibialis anterior muscle in the side ipsilateral to mechanical pressure（5.89 N）, andthe area of integrated EMG for 1s was measured as the magnitude of EMG activity. In theLOX group（n＝12）, the magnitude of EMG activity significantly decreased at 40 min followingapplication of the plaster, whereas the magnitude of EMG activity in the Base group didnot produce any change. This result suggests that LOX can produce analgesia on muscle painwithin 40 min after application of plaster containing LOX.（Jpn Pharmacol Ther 2009；37：165−70）KEY WORDS Loxoprofen sodium, Electromyogram（EMG）, Muscle pain, Analgesia