Tri-mix is a mixture of Papverine plus two prostaglandins (Phentolamine and Alprostadil). This combination of medications work well together resulting in good erectile function for many patients. This mix uses smaller amounts of the prostaglandins, which can lead to pain in large amounts. The combination of the higher potency with less of the prostaglandins makes this a great starting injection and the most commonly prescribed.

1. Papaverine: A drug that causes blood vessels to expand (vasodilator); it produces an erection by allowing for increased blood flow to the penis. Papaverine results in increased erectile capacity by relaxation of penile smooth muscle. This drug was one of the first effective therapies for erectile dysfunction administered by penile injection.
2. Phentolamine: is classified as an Alpha-Adrenoceptor Antagonists. When injected into the penis, it induces an erection by relaxing and dilating the blood vessels of the penis, as well as by elevating cardiac output. It also effects the smooth muscle tone of the penile tissues by keeping the corpora cavernosa in a contracted state.
3. Prostaglandin E1 (Alprostadil): A potent hormone-like substance that induces erection by relaxing the penis's blood vessels and dilating cavernosal arteries- allowing for more blood into the penis and less blood out.