In one aspect of the present invention there is provided a therapeutic composition comprising a proportion of a drug of the following formula: ##STR5## in which A is oxygen, a methylene group or an ethylene group, the full line embracing a broken line is either a single or a double bond, R is a member selected form phenyl, phenyl substituted with a halogen a, C1 to C4 alkoxy, a trifluoromethyl, a