Which PDE-5 inhibitor for erectile dysfunction?

A substance called cyclic GMP, when released, dilates the blood vessels in the penis, which leads to an erection. Cyclic GMP is broken down by an enzyme called phosphodiesterase type 5 (PDE-5). This is why medications that inhibit PDE-5 increase the effect of cyclic GMP and increase penile erections. These medications are first-line treatments for…