Talk to your doctor about which dosing schedule is right for you. Tadalafil does not prevent pregnancy or the spread of sexually transmitted diseases such as human immunodeficiency virus HIV. Usually, doctors start patients off at a dose of 10 mg and then drop it down or increase it depending on how the patient does. Introduction In the age of e-commerce and digital advancements, more and more consumers are shifting to online platforms for their purchases. The drug works by increasing blood flow to the penis, thus aiding in achieving an erection. It lasts 4 to 5 hours, or longer if you have mild to moderate ED.People who are taking tadalafil for erectile dysfunction may be able to continue taking alpha blockers. Talk to your doctor for more information. Vision problems: If you experience a . While some countries sell Viagra over-the-counter, in the United States, Viagra and similar ED medications like sildenafil, Cialis, and tadalafil, require a prescription from a licensed doctor. Tadalafil (Cialis) is used to treat erectile dysfunction (ED, impotence; inability to get or keep an erection), and the symptoms of benign prostatic hyperplasia (BPH; an enlarged prostate) which include difficulty urinating (hesitation, dribbling, weak stream, and incomplete bladder emptying), painful urination, and urinary frequency and urgency in adult men.