Very clinically major. Prevent combos; the potential risk of the interaction outweighs the advantage.If you take tadalafil for pulmonary arterial hypertension, usually do not just take Cialis® or other PDE5 inhibitors, such as sildenafil (Revatio® or Viagra®) or vardenafil (Levitra®). Cialis® also has tadalafil. If you are taking an excessive