Megalis 20 mg belongs to the class of drugs called PDE5 (phosphodiesterase type 5) inhibitors. During sexual arousal, nitric oxide is released in the penile tissues, which increases levels of cyclic guanosine monophosphate (cGMP). This chemical relaxes smooth muscles in blood vessels and increases blood flow to the pill. Tadalafil works by blocking the PDE5 enzyme, which normally breaks down cGMP, allowing its effects to last longer and support a stronger erection response. https://www.genericday.com/megalis-20-mg.html