PURPOSE: To use 1,5-benzothiazepine compounds, 1,6-benzothiazocine compounds, or their acid addition salts, as an antiulcer agent taking advantage of its strong effect to suppress the secretion of gastric juice.

CONSTITUTION: The compound of formula (R is H or CHO; n is 3 or 4) or its acid addition salt is used as an antiulcer agent. The compound of formula is 1,5-benzothiazepine compound when n is 3, and 1,6-benzothiazocine compound when n is 4. It has been found that both of them have strong activity to suppress the secretion of gastric juice. The compound suppresses the pH, the secretion of juice, and the secretion of acid in the stomach, and is useful as an antiulcer agent. Concrete examples of the compound of formula are 1,6-benzothiazocine, 1,5-benzothiazepine hydrochloride, etc. Dose; 5W75mg per dose for adult by oral administration, 3W4 doses daily.