Phosphodiesterase type 5 (PDE 5) inhibitors are a class of medications that include Sildenafil, which is found in PENEGRA 100MG. It is applied to the treatment of male impotence. When a man has erectile dysfunction, commonly referred to as impotence, he is unable to maintain the strong erection needed for regular sexual intercourse. It occurs when the blood arteries supplying the penis have narrowed, resulting in decreased blood flow to the penis.