Vidalista 20mg (Tadalafil) 20mg is a prescription medicine taken by mouth for the treatment of erectile dysfunction (ED) in men. ED is a condition where the penis does not harden and expand when a man is sexually excited, or when he cannot keep an erection. A man who has trouble getting or keeping an erection should see his doctor for help if the condition bothers him. Vidalista may help a man with ED get and keep an erection when he is sexually excited.