Sildenafil citrate salt belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors. Sildenafil Citrate Fildena XXX 100 is an active ingredient found in chewable tablets. Sildenafil citrate is a chemical compound used in drugs that treat erectile dysfunction and pulmonary hypertension.In pulmonary hypertension it works by relaxing blood vessels in the lungs and increasing blood flow to the pulmonary arteries.