This is a serious condition that requires immediate medical attention. There may be rare occurrences of priapism or painful, prolonged erections. Talk to your doctor about eating grapefruit and drinking grapefruit juice while taking this medicine. The table below summarizes the typical dosages for tadalafil: Indications of Tadalafil:. Your doctor will help you decide the best time for you to take tadalafil before sexual activity. Before taking tadalafil, tell your doctor and pharmacist if you are allergic to tadalafil, any other medications, or any of the ingredients in tadalafil tablets. The drug is approved for use in adults.1. What is Cialis used to treat? Cialis is approved for the treatment of men who experience difficulty having and maintaining an erection (impotence). 2. How does Cialis work? . Tadalafil is its active ingredient and is available as a generic drug. The FDA has approved Cialis to treat ED, symptoms of BPH, or combined ED and BPH in males .  · Description and Brand Names Drug information provided by: Merative, Micromedex ® US Brand Name Adcirca Cialis Descriptions Tadalafil is used to treat .