<unk> (topical) is a vasodilator that is FDA approved for the treatment of to regrow hair on the top of the scalp in men.   Common adverse reactions include scalp irritation or redness and unwanted facial hair growth.
Minoxidil 
Endralazine
Alprostadil 
Nitroprusside
Isosorbide dinitrate
Balsalazide
Nadolol 
Captopril