Sildenafil citrate in Fildena Double is a phosphodiesterase kind five (PDE5) inhibitor. It works with the aid of blockading the motion of PDE5, an enzyme that breaks down cyclic guanosine monophosphate (cGMP). cGMP is a molecule that performs a essential function in enjoyable and dilating the blood vessels in the penis. By inhibiting PDE5, sildenafil permits cGMP to accumulate, merchandising multiplied blood go with the flow to the penis.