Because it works so well to cure erectile dysfunction, kamagra 100mg is a drug that has become very popular. The active component of it is sildenafil citrate, which is also found in the well-known ED drug Viagra. As a phosphodiesterase type 5 (PDE5) inhibitor, sildenafil citrate facilitates the relaxation of the penile blood vessels, increasing blood flow and ultimately producing a hard erection.