{HEAD ~ A method} of treating male erectile dysfunction comprising administering to a male human in {TAIL ~ need} of such treatment an effective amount of a compound of formula : ##STR6## wherein R1 is methyl or ethyl R2 is ethyl or n propyl 
{ HEAD ~ A method } of treating male erectile dysfunction comprising administering to a male human in { TAIL ~ need } of such treatment an effective amount of a compound of formula : # # STR6 # # wherein R1 is methyl or ethyl R2 is ethyl or n propyl
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