Manforce 100 mg belongs to a group of medications known as phosphodiesterase type 5 (PDE5) inhibitors. These drugs work by blocking the PDE5 enzyme, which usually breaks down cyclic GMP, a substance responsible for relaxing blood vessels. When PDE5 is inhibited, cyclic GMP levels rise, which leads to the relaxation of blood vessels in the penis and allows increased blood flow. This, in turn, helps men achieve and maintain an erection when sexually stimulated.