What is the difference between Tadalafil and Sildenafil?

Both Tadalafil and Sildenafil are part of the same class of medication, called PDE-5 inhibitors. The main difference between Tadalfil and Sildenafil is how long they last. Tadalafil can last up to 36 hours whereas Sildenafil usually lasts for around 4 to 6 hours.