Fildena is a medication used to treat erectile dysfunction (ED) in men. Its active ingredient is sildenafil citrate, which works by increasing blood flow to the penis during sexual stimulation. Sildenafil citrate is a phosphodiesterase type 5 (PDE5) inhibitor. PDE5 is an enzyme found in the smooth muscle cells of the blood vessels in the penis. It breaks down cyclic guanosine monophosphate (cGMP), a molecule that promotes relaxation of smooth muscle cells and dilation of blood vessels. By inhibiting PDE5, sildenafil increases the levels of cGMP in the penis, leading to smooth muscle relaxation and increased blood flow. Increased levels of cGMP cause the smooth muscle cells in the blood vessels of the penis to relax, allowing these blood vessels to dilate. This dilation allows more blood to flow into the penis, resulting in an erection when the man is sexually aroused. Fildena helps maintain an erection by preventing the degradation of cGMP. Normally, after ejaculation or when sexual stimulation stops, the enzyme PDE5 breaks down cGMP, causing the smooth muscle cells in the penis to constrict and blood flow to decrease. However, since sildenafil inhibits PDE5, it prolongs the effects of cGMP, allowing the erection to be maintained for a longer period. It's important to note that Fildena (sildenafil) doesn't automatically cause an erection; sexual stimulation is still necessary for it to work. Additionally, it's essential to use Fildena as prescribed by a healthcare provider and to follow all safety instructions.