Compounds of general formula (I) wherein R1 is selected from any one of phenyl, pyridinyl, thienyl, furanyl, imidazolyl, pyrrolyl and triazolyl; where each R1 phenyl ring and R1 heteroaromatic ring may optionally and independently be further substituted by 1, 2 or 3 substituents selected from straight and branched C1–C6 alkyl, NO2, CF3, C1–C6 alkoxy, chloro, fluoro, bromo, and iodo. The substitutions on thephenyl ring and on the heteroaromatic ring may take place in any position on said ring systems; are disclosed and claimed in the present application, as well as their pharmaceutically acceptable salts and pharmaceutical compositions comprising the novel compounds and their use in therapy, inparticular in the management of pain.