Sildenafil Oral Jelly 100mg is a phosphodiesterase type 5 (PDE5) inhibitor that contains sildenafil. Sildenafil Oral Jelly 100mg increases blood flow into the penis, which is required to cause an erection. Nitric oxide is released in the erectile tissue of the penis during sexual stimulation, which activates the enzyme guanylate cyclase. This enzyme causes an erection by increasing the amounts of a substance called cyclic guanosine monophosphate (cGMP), which relaxes the blood arteries in the penis and allows blood to fill the spongy erectile tissues. Phosphodiesterase type 5 (PDE5) is another enzyme that breaks down cGMP, restricting blood flow into the penis and resulting in erection loss.