Would you consider to use the propensity score matching? According to your statement, I think that using proc psmatch might be helpful. For example: proc psmatch data=drugs region=cs;
class Drug Gender;
psmodel Drug(Treated='Drug_X')= Gender Age Bmi;
match method=exact(k=5) exact=Gender stat=lps caliper=0.25;
assess lps var=(Gender Age Bmi) / weight=none plots=(boxplot barchart);
output out(obs=match)=Outgs lps=_Lps matchid=_MatchID; In the match statement, you can assign method=exact, k=5 for your situation.
... View more