Abstract: Novel compounds of the formula or a pharmaceutically acceptable salt or solvate thereof, wherein: the dotted line represents an optional double bond; X1 is optionally substituted alkyl, cycloalkyl, aryl, heteroaryl or heterocycloalkyl; X2 is —CHO, —CN, optionally substituted amino, alkyl, or aryl; or X1 is optionally substituted benzofused heterocyclyl and X2 is hydrogen; or X1 and X2 together form an optionally benzofused spiro heterocyclyl group R1, R2, R3 and R4 are independently H and alkyl, or (R1 and R4) or (R2 and R3) or (R1 and R3) or (R2 and R4) together can form an alkylene bridge of 1 to 3 carbon atoms; Z1 is optionally substituted alkyl, aryl, heteroaryl, cycloalkyl or heterocycloalkyl, or —CO2(alkyl or substituted amino) or CN; Z2 is H or Z1; Z3 is H oralkyl; or Z1, Z2 and Z3, together with the carbon to which they are attached, form bicyclic saturated or unsaturated rings; pharmaceutical compositions therefore, and the use of said compounds as nocicepti