Tadalafil 20 is used to treat men who have problems with sexual impotence. Tadalista 20 belongs to a group of drugs known as Phosphodiesterase 5 (PDE5) inhibitors. These drugs inhibit the enzyme called Phosphodiesterase type-5 from working quickly. For erectile dysfunction, take 1 tablet at least 30 minutes before you want to have sex. If you are taking tadalafil for prostate enlargement, you can take your tablet in the morning or in the evening, but it is best to take it at the same time each day.