<unk> (Topical ointment) is a colorectal agent that is FDA approved for the treatment of moderate to severe pain associated with chronic anal fissure..   Common adverse reactions include hypotension, flushing, dizziness, headache, lightheadedness..
Nitroglycerin 
Nitroprusside
Endralazine
Imolamine
Amrinone
Papaverine
Adenosine
Nadolol 