Pharmacology · 4 min read
Nitric oxide, cGMP, and the enzyme that ED tablets block.
During arousal, nerves release nitric oxide in penile tissue. Nitric oxide triggers production of cGMP, which relaxes smooth muscle and lets blood flow in.
PDE5 is the enzyme that breaks cGMP down. Blocking it lets cGMP build up, sustaining smooth-muscle relaxation and blood flow. This is why PDE5 inhibitors support, but do not create, an erection.
Sildenafil citrate
Well-established prescription PDE5 inhibitor with predictable on-demand use.
Tadalafil
Long-duration PDE5 inhibitor with both daily and on-demand dosing options.
Vardenafil hydrochloride
Established PDE5 inhibitor similar to sildenafil, with a distinctive QT-interval warning.
Avanafil
FDA-approved PDE5 inhibitor with a fast onset but less long-term real-world data.