Long-Lasting Muscle Relaxant Effect of Patch Containing Centrally Acting Muscle Relaxant

Due to its profound intestinal first-pass metabolism, oral eperisone hydrochloride produces a very low bioavailability and a very short muscle relaxant activity. To improve the efficacy and compliance of eperisone, we designed a new dosage form, the transdermal patch and evaluated the muscle relaxant effects of this patch in rats. The muscle relaxant activity was assessed by measurement of forelimb grip strength and hanging test in rats. The transdermal patch of eperisone hydrochloride showed significant muscle relaxant activity at 0.5, 1.5 and 3 cm$^2$/200 g rat (1.39, 4.17 and 8.33 mg of eperisone hydrochloride/kg, respectively) in a dose-dependent manner and the effects were lasted over 24 hours. The oral eperisone hydrochloride showed significant activity at 12.5, 25 and 50 mg/kg in a dose-dependent manner but the activity was within 1 or 2 hours after administration. These results suggest that the eperisone hydrochloride is absorbed efficiently from transdermal patch and the patch can exert potent and long-lasting muscle relaxant activity. This transdermal patch will increase the efficacy and compliance in the clinical use of eperisone hydrochloride.

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