Papervine and Phentolamine
“Adding papaverine and phentolamine to the alprostadil regimen synergistically increases arterial blood flow via separate mechanisms. Papaverine relaxes the sinusoid and the smooth muscle of the helicine arteries, while phentolamine relaxes arterial smooth muscle and blocks the alpha-adrenergic receptors that inhibit an erection.”
Looks like papervine and phetolamine have more uses than what is stated on this forum.