Cialis works by enhancing the effects of one of the chemicals the body normally releases into the penis during sexual arousal. Side effects Side effects of oral ED medicines are often mild. Dosing Guidelines Typical Cialis dosages will differ depending on the conditions it’s prescribed to treat as well as other factors. The medication was developed by U. The drug is approved for use in adults. It might work longer if you have mild to moderate erectile dysfunction. How oral medicines differ Each oral medicine for ED has a slightly different chemical makeup.Cialis (tadalafil) is an orally administered prescription medication used for erectile dysfunction (ED) and pulmonary arterial hypertension (PAH) to reduce the symptoms of an enlarged prostate. Before starting tadalafil, tell your provider about your current medications (prescription and over-the-counter [OTC]) and any vitamins or. Oral medications, like Viagra and Cialis, which require a prescription and are commonly used to treat ED, can take 30 minutes to take effect, she adds. Injections take less time to work, but they. The lowest GoodRx price for the most common version of Tadalafil (Cialis) is around $, 96% off the average retail price of $ Read more about Tadalafil (Cialis) .