Sildenafil citrate, the active ingredient in Kamagra 100 mg, is a phosphodiesterase type 5 (PDE5) inhibitor. It works by increasing blood flow to the penis, allowing men to achieve and maintain erections when sexually stimulated.Kamagra 100 mg is one of the standard dosages available for sildenafil and is commonly prescribed to men with ED. It is typically taken about 30 minutes to an hour before anticipated sexual activity and can remain effective for up to four hours.