For treatment of erectile dysfunction daily use : Adults—2. Take tadalafil exactly as directed. Your doctor may need to change the doses of your medications or monitor you carefully for side effects. There is a problem with information submitted for this request. Nitrates come as tablets, sublingual under the tongue tablets, sprays, patches, pastes, and ointments. Tadalafil has been extensively studied for ED.Is 40 mg of Cialis safe? Taking 40 mg of Cialis could be dangerous and raise the risk of side effects such as a sudden drop in blood pressure and priapism. The .  · Adults—5 milligrams (mg) once a day, taken at the same time each day, without regard for the timing of sexual activity. Children—Use is not recommended. For . Efficacy Dosing Guidelines Cialis is a prescription medication containing the active ingredient tadalafil. Cialis belongs to a group of medications known as .