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Compounds of formula (1), salts and pro-drugs wherein: R1, R2, R3 and R4 are hydrogen, alkyl, hydroxyalkyl, halogen, haloalkyl, alkoxy, haloalkoxy, alkoxycarbonyl, carboxyl, hydroxyl, nitro, amino, monalkylamino, dialkylamino, acylamino, alkoxycarbonylamino, alkylsulphonyl, arylsulphonyl, alkylsulphonylamino, arylsulphonylamino, aminosulphonyl or cyano, or any two of R1 to R4 that are adjacent on the ring may together represent the moiety -O-(CH2)n-O- wherein n is 1 to 3; R5 is hydrogen or alkyl; R6 is hydrogen or alkyl; and X is selected from the group consisting of: (a) groups of formula OR7 wherein R7 is hydrogen or alkyl which is optionally substituted with a substituent selected from alkylsulfonylalkyl, saturated or partially unsaturated heterocyclic, alkoxy, carboxyl, nitro, amino, monalkylamino, dialkylamino, halogen, and alkoxycarbonyl, provided that when R7 is hydrogen or ethyl, then R1, R2, R3 and R4 cannot be selected from hydrogen, halogen and alkyl; and (b) groups of formula NR8R9 wherein R8 and R9 together with the nitrogen atom to which they are attached form a saturated or partially unsaturated heterocyclic group which optionally contains at least one more heteroatom selected from nitrogen, oxygen and sulphur atoms, said saturated or partially unsaturated heterocyclic group optionally further being substituted by one or more substituents selected from alkyl, halogen, haloalkyl, alkoxy, alkoxycarbonyl, carboxyl, nitro, amino, monalkylamino, dialkylamino and hydroxyl, provided that: (i) when R8+R9+N=piperazine, and 1 of R1 to R4 are hydrogen, hydroxyl, nitro, amino, alkylamino, dialkylamino, alkoxycarbonylamino, halogen, alkoxy or alkyl, the nitrogen atom at the 4-position of the piperazine is not alkyl substituted, (ii) when each of R1, R2, R3, R4, R5 and R6 is hydrogen, X is not unsubstituted piperazinyl or unsubstituted morpholino, (iii) when each of R1, R2, R4, R5 and R6 is hydrogen and R3 hydrogen, bromine or hydroxyl, X is not methoxy, (iv) when each of R2 and R3 is methoxy or they together represent -O-CH2-O- and each of R1, R4, R5 and R6 is hydrogen, X is not unsubstituted piperidine, are Cavx channel blockers and are of use in the treatment of various conditions including pain.