Malegra 25 mg works by inhibiting the enzyme phosphodiesterase type 5 (PDE5). This enzyme breaks down cyclic GMP (cGMP), a molecule that helps relax the smooth muscles and widen the blood vessels in the penis. When PDE5 is inhibited, cGMP levels are elevated, promoting increased blood flow to the penis, which helps men achieve and sustain an erection when sexually aroused.