Tri-Mix is an injectable three-drug prescribed medication used to treat erectile dysfunction. The active ingredients in the mixture are usually alprostadil, papaverine, and phentolamine. Bi-Mix & Quad-Mix
The injection must be compounded by a pharmacy and administered via intracavernosal injection (an injection at either side, not the base, of the penis). Trimix is typically compounded by a pharmacy in a sterile environment and then frozen. 
A Prescription is Required.