The active ingredient in Malegra 100 mg is Sildenafil Citrate, a phosphodiesterase 5 inhibitor. It works by opening blood vessels to the penis, which improves blood circulation. Moreover, it also relaxes penile muscles, which promotes prolonged erections. However, you must consult your doctor before using this medication because it may cause serious side effects. This is a prescription-strength medicine and should be taken under the guidance of a healthcare professional.