Tadalista 20 mg is a medication that contains tadalafil, which is used to treat erectile dysfunction (ED) in men. Its mechanism of action can be understood more easily by breaking it down into a few simple steps. When a man is sexually aroused, the body naturally releases a chemical called nitric oxide (NO) in the penis. This chemical activates another substance in the body called cyclic guanosine monophosphate (cGMP). cGMP causes the smooth muscles in the blood vessels of the penis to relax, which allows more blood to flow into the penis, leading to an erection.