Malegra 100 Mg Sildenafil is prescribed to men to treat erectile dysfunction (impotence). Erectile dysfunction is the inability to obtain and maintain a firm enough erection for sexual activity. Sildenafil Citrate is the main active ingredient of Malegra 100 Mg Tablet, which belongs to a family of drugs called phosphodiesterase-5 (PDE-5) inhibitor. This medicine works by preventing the action of a chemical in your body, called phosphodiesterase type-5. This helps to relax blood vessels and increases blood flow to particular areas of the body.