Quadmix is used to treat erectile dysfunction in men and consists of four medications from complementary drug classes that work together for enhanced effectiveness. This sterile injectable solution contains Papaverine, Phentolamine, Alprostadil and Atropine. Papaverine is a vasodilator that promotes erections by widening blood vessels and increasing blood flow to the penis. The second component, Phentolamine—an alpha-adrenoceptor antagonist—supports erection by relaxing and expanding the blood vessels in the penis and boosting cardiac output. Noradrenaline normally maintains penile smooth muscle contraction by keeping the corpora cavernosa in a tightened state, and Phentolamine helps counteract this effect to facilitate an erection. The third component, Alprostadil, is a prostaglandin analog, a vasodilator frequently prescribed by healthcare professionals to treat erectile dysfunction (ED or impotence). It works by relaxing and expanding the walls of the blood vessels (arteries), promoting increased blood flow. Alprostadil replicates a naturally occurring substance in the body that helps maintain open blood vessels. The last component, Atropine functions by blocking receptors in the nervous system that regulate the relaxation of smooth muscle. As an anticholinergic agent, it reduces the cholinergic inhibition of adrenergic activity and the cholinergic stimulation of nonadrenergic, noncholinergic pathways involved in controlling neurogenic relaxation of the smooth muscle in the corpora of the penis. Quadmix is administered directly into the shaft of the penis using a very fine needle. It is effective for 1 to 2 hours.