Fildena Chewable 100 mg, like other medications containing sildenafil citrate, works to treat erectile dysfunction (ED) by improving blood flow to the penis. Here’s how Fildena Chewable 100 works: Inhibition of PDE5: Inside the penis, there’s an enzyme called phosphodiesterase type 5 (PDE5). In men with ED, PDE5 can break down a chemical called cyclic guanosine monophosphate (cGMP), which plays a role in relaxing and dilating blood vessels in the penis. This, in turn, restricts blood flow to the area.