Subsequently, the FDA approved both vardenafil [27] and tadalafil in It works for up to 36 hours. Its effects often last for 4 to 5 hours. You can buy it from a store-based pharmacy or reputable online pharmacy with a prescription. This medicine also works best when you take it an hour before sex on an empty stomach. A newer form of the medicine that dissolves on the tongue might work faster than the pill that you swallow.Tadalafil Brand names: Cialis, Adcirca. Tadalafil. Find out how tadalafil treats erectile dysfunction, pulmonary hypertension and benign prostate enlargement, and how to take it. Cialis is only available by prescription in the United States. Viagra: Additionally, a study from Trusted Source. found that combining L-arginine and sildenafil (Viagra) worked better for. Introduction If you’re looking at treatment options for erectile dysfunction (ED), you may want to learn more about Cialis and its cost. It’s a prescription drug used to treat .