Both Viagra (Sildenafil) and Cialis (Tadalafil) are PDE5 inhibitors that improve blood flow to certain tissues. Both are also approved for the use in increasing the ability of people with Pulmonary Arterial Hypertension (high blood pressure) to exercise. Tadalafil is also approved as treatment in reducing a particular kind of prostate inflammation which relieves pain during urination and improves urination frequency while reducing urgency. #onthisday #history #throwback #ed #cialis #medicalhisto