Tadalafil, a component of Tadalista 20, belongs to the group of medications called phosphodiesterase type 5 inhibitors. By relaxing the blood vessel muscles in the penis, it improves blood flow and induces an erection. It is typically taken 30–60 minutes before sexual activity and has a 36-hour maximum duration of action. It's a medicine that can bring on and maintain an erection with sufficient sexual stimulation. Some of the side effects of using it include headaches, blurred vision, upset stomachs, stuffy noses, back discomfort, and flushing in the face, neck, or chest.