I never use any of these products, but a simple Google search will show you that Kamagra just contains the same chemical that Viagra does; Sildenafil.
Viagra is a tablet and Kamagra is a gel but that makes no difference.
You swallow either one so it has to go into your stomach and then gradually be absorbed into your blood stream.
If you have to use drugs then go to your doctor and get a prescription for Viagra and then buy it from your chemist.
Why go on the net and buy from a dodgy bastard who will charge you big money and could be selling you rat poison or bicarb of soda?