The cGMP is primarily responsible for increasing the size of the blood vessels carrying blood to and from the penis.. Vardenafil prevents cGMP from being destroyed early so erection persists longer. The mechanism of action of Tadalafil is the same as Viagra (Sildenafil) and works by blocking an enzyme called PDE 5 which helps the smooth muscles in the penis to relax, thereby increasing blood flow to the penis. Sildenafil tadalafil softabs prevents the destruction of an enzyme cGMP and allows cGMP to accumulate and persist longer. The longer cGMP persists, the more prolonged the engorgement of the penis Nitric oxide in the bloodstream activates an enzyme, cyclic guanosine monophosphate (cGMP). Dapoxetine belongs to a class of medicines known as Selective daily tadalafil Serotonin Reuptake Inhibitors (SSRI) which inhibits the uptake of serotonin in the neural cells. The inhibition of Serotonin uptake inhibits the apcalis tadalafil jelly 5 ml 40 sachets ejaculatory expulsion of reflex to the brain, thereby preventing premature ejaculation in men. For ejaculation to happen in men, a reflex has to be passed on to the brain via the sympathetic nervous system.