Starting from 3-substituted-1,2,4-triazole-5-thiones (1a-h), eight new 5-carbomethoxy-2-substituted-7H-1,2,4-triazolo[3,2-b]1,3-thiazine-7-ones (2a-h) were synthesized and characterized by spectral and elementary analysis. The obtained compounds were submitted to preliminary pharmacological assay to evaluate their antiinflammatory and analgesic activities as well as gastrointestinal irritation liability and acute toxicity. Among the compounds studied, compounds 2c, 2d, 2e and 2h showed most remarkable antiinflammatory activity in the carrageenan and serotonin induced edema and in the inhibition of castor oil-induced diarrhea tests. The analgesic activity of these active compounds correlated with their antimflammatory activities in the inhibition of acetic acid-induced writhing test. In gastric ulceration studies, the compounds were found safety at low dose levels (10 and 20 mg/kg). (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.