Compounds of formula I: ##STR00001## and pharmaceutically-acceptable salts thereof, wherein Q, Ar.sup.1, A and Ar.sup.2 are as defined in the specification, pharmaceutical compositions and formulations containing them, methods of using them to treat diseases and conditions either alone or in combination with other therapeutically-active compounds or substances, processes and intermediates used to prepare them, uses of them as medicaments for therapy, uses of them in the manufacture of medicaments and uses of them for diagnostic and analytic purposes.