Penegra 50 mg is a phosphodiesterase type 5 (PDE5) inhibitor. PDE5 is an enzyme that breaks down a substance called cGMP (cyclic guanosine monophosphate) in the body. cGMP is important for relaxing the smooth muscles in the blood vessels of the penis, which allows blood to flow in and cause an erection. By inhibiting PDE5, Penegra 50 mg helps maintain higher levels of cGMP, thereby increasing blood flow and enabling an erection during sexual stimulation.