Abstract
Effects of tizanidine, a centrally acting muscle relaxant, on gastric acid secretion and gastric ulcers were studied in the rat. Tizanidine (5 mg/kg, s.c.) did not influence basal acid secretion, but inhibited the centrally stimulated acid secretion in anesthetized rats. Intraduodenal administration of tizanidine (10 mg/kg) also inhibited the centrally stimulated acid secretion. The compound potentiated bethanechol-induced acid secretion at 10 mg/kg, s.c. Clonidine was found to have similar effects to tizanidine at the lower dose. Both tizanidine and clonidine inhibited basal acid secretion at a relatively low dose in conscious rats. Tizanidine (5 mg/kg, s.c.) did not modify indomethacin and stress-induced ulcers, but Shay ulcers were slightly inhibited by the drug. Indomethacin ulcers were significantly inhibited by 10 mg/kg, s.c., 10 mg/kg, p.o. or 20 mg/kg, p.o. of tizanidine. Clonidine also was found to be a strong inhibitory agent of indomethacin-, stress and Shay-ulcers. These results suggest that similar to clonidine, a high dosage of tizanidine influences gastric acid secretion and gastric ulcers, although the activity is lower than that of clonidine.
