Compounds of the formula ##STR00001## where the variables are defined in the specification have cytochrome P450RAI-1 and P450RAI-2 inhibitory activity, and are suitable for treatment of mammals with conditions which are treatable with retinoids, or which are controlled by or responsive to the organism's native retinoic acid. Formulations containing the compounds of the invention can also be co-administered with retinoids and/or Vitamin A to enhance or prolong the effects of medications containing retinoids, Vitamin A, or of the organism's native retinoic acid.