For Kamagra, since it is using the same active ingredient, the activation time should be similar. Avanafil Stendra. It might work longer if you have mild to moderate erectile dysfunction. The key pharmaceutical ingredient behind this action is called sildenafil citrate, which is present in several medications and branded under different names to breach the market and get a patent. These include Cialis Tadalafil , Spedra Avanafil , and Levitra Vardenafil , which are also PDE5 inhibitors that work in a similar way to sildenafil and are also available online in tablet form on prescription.Sildenafil (Viagra). This medicine works best when you take it on an empty stomach an hour before sex. The body takes longer to absorb it after a high-fat meal or .  · Cialis vs Viagra – What’s the difference between them? Do you know these 11 amazing facts about Viagra? Is generic Viagra available in the U.S.? View more FAQ.  · Viagra; Descriptions. Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines .