Definition: (fen-TOLE-a-meen) Given by injection, it causes blood vessels to expand (vasodilator), thereby increasing blood flow. When injected into the penis, it increases blood flow to the penis,which results in an erection.
When used in combination with papaverine it is a bi-mix When prostaglandin E-1 is added it is a trimix.
It is sometimes misspelled as phentolOmine.
There is an extensive section at Phoenix5 dealing with injections.