Tadacip 20 contains the active substance Tadalafil. It belongs to a group of drugs called PDE5 (Phosphodiesterase-5) inhibitors. It is an effective oral medication for the treatment of erectile dysfunction (commonly referred to as impotence). The effects of this tablet begin within 15 minutes of taking the drug and last for 36 hours after taking it. It is best to take it 30 minutes or 1 hour before sexual activity.