The present invention relates to compounds of formula (I), wherein n is zero, 1, 2 or 3; R represents C 1-6 alkyl, C 1-6 alkoxy, hydroxy, halogen, cyano, trifluoromethyl SO 2 C 1-6 alkyl, NR. sup.a R b, NR a COR b or CONR a R b, where R a and R b are each H, C 1-4 alkyl, phenyl or trifluoromethyl; R. sup.1 represents phenyl optionally substituted by 1, 2 or 3 of C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 3-7 cycloalkyl, C 3-7 cycloalkylC 1-4 alkyl,--O(CH 2) p O--(where p is 1 or 2) , halogen, cyano, nitro, trifluoromethyl, trimethylsilyl, OR a, SR. sup.a, SOR a, SO 2 R a, NR a R b, NR a COR b, NR a CO 2 R b, COR a, CO 2 R a or CONR a R. sup.b ; naphthyl; benzhydryl; or benyl, where the naphthyl group or each phenyl moiety of benzyl and benzhydryl may be substituted by C 1-6 alkyl, C 1-6 alkoxy, halogen or trifluoromethyl; R 2 represents hydogen, a substituent as defined for R 1 or heteroaryl selected from indazolyl, thienyl, furanyl, pyridyl, thiazolyl, tetrazolyl and quinolinyl; wherein each heteroaryl may be substituted by C 1-6 alkyl, C 1-6 alkoxy, halogen or trifluoromethyl; R 3 and R 4 are each H or C 1-6 alkyl or R 3 and R 4 together are linked so as to form a C 1-3 alkylene chain; R 5 represents H, C 1-6 alkyl, C 3-7 cycloalkyl, C 3-7 cycloalkylC 1-4 alkyl, phenylC. sub.1-4 alkyl, CO 2 R a, CONR a R b, SOR a or SO 2 R a, wherein the phenyl moiety may be substituted by C. sub.1-6 alkyl, C 1-6 alkoxy, halogen or trifluoromethyl; X and Y are each H, or together represents =O; and Z represents a bond, O, S, SO, SO 2, NR 6, or--(CR 6 R 6)--where R 6 is H or C. sub.1-6 alkyl; or a pharmaceutically acceptable salt thereof. The compounds are of particular use in the treatment or prevention of pain, inflammation, migraine, emesis and postherpetic neuralgia. STR1