A method for the treatment of cerebrovascular disorders and/or disorders associated with cerebral senility and/or other disorders which method comprises the administration of an effective, non-toxic amount of a compound of formula (I): ##STR1## or if appropriate a pharmaceutically acceptable salt thereof, wherein R.sup.1 and R.sup.2 each independently represent alkyl or a moiety of formula (a): --(CH.sub.2).sub.m --A (a) wherein m represents zero or an integer 1, 2 or 3; A represents a substituted or unsubstituted cyclic hydrocarbon radical; andR.sup.3 represents a halogen atom, a nitro group, or a group --NR.sup.4 R.sup.5 wherein R.sup.4 and R.sup.5 each independently represents hydrogen, alkyl or alkylcarbonyl or R.sup.4 and R.sup.5 together with the nitrogen to which they are attached forming an optionally substituted, heterocyclic group; certain novel compounds falling within formula (I) and compositions comprising such compounds.