Silagra 100mg contains sildenafil, a phosphodiesterase type 5 (PDE5) inhibitor that reacts on the erectile tissue of the penis to raised blood flow, which is needed to cause an erection. During sexual stimulation nitric oxide is resting the erectile tissue of the penis which activates the enzyme guanylate cyclase. This enzyme high levels of a chemical called cyclic guanosine monophosphate (cGMP), which relaxes the blood vessels in the penis and allows blood to fill the spongy erectile tissues to cause an erection. Another enzyme called phosphodiesterase type 5 (PDE5) breaks down cGMP stopping blood flow into the penis, which causes loss of an erection. this medicine inhibits the action of PDE5 which resolves erectile dysfunction by allowing the natural process of sexual stimulation to activate the cGMP mechanism for achieving and maintaining an erection.