IMIDAZOLDERIVATE

Tricyclic imidazole derivatives of the formula I wherein R1 is 2-pyridyl optionally substituted by lower alkyl or lower alkoxy, n is the integer 0 to 1, R2 is hydrogen or lower alkyl, R3 and R4, independently, are hydrogen or lower alkyl, A is a group of the formula +TR m is the integer 2 or 3, R5, R6, R7 and R8, independently, are hydrogen or lower alkyl, and R9 is hydrogen and R10 is hydrogen or lower alkyl or R9 and R10 taken together are oxo, provided that at least one of R3 and R4 is lower alkyl when A is a group of the formula -CH=CH-CH=CH- or -(CH2)4-, and their pharmaceutically acceptable acid addition salts. The compounds of formula I inhibit gastric acid secretion and prevent the formation of gastric ulcers.