For treatment of erectile dysfunction and benign prostatic hyperplasia daily use : Adults—5 milligrams mg once a day, taken at the same time each day, without regard for the timing of sexual activity. Also, do not stop taking this medicine without checking first with your doctor. The following information includes only the average doses of this medicine. Keep out of the reach of children. For oral dosage form tablets : For treatment of benign prostatic hyperplasia daily use : Adults—5 milligrams mg as a single dose, no more than once a day, taken at the same time each day. For treatment of pulmonary arterial hypertension: Adults—40 milligrams mg two 20 mg tablets taken once a day. May make this condition worse.Don’t take more than one dose of tadalafil (Cialis) unless instructed by your provider. Doing so could lead to more side effects like low blood pressure, dizziness, and vision problems. If you get muscle or back pain with tadalafil (Cialis), it .  · Cialis® also contains tadalafil. If you take too much tadalafil or take it together with these medicines, the chance for side effects will be higher. If you experience a prolonged erection for more than 4 hours or a painful erection for more than 6 hours, contact your doctor immediately. Cialis® also contains tadalafil. If you take too much tadalafil or take it together with these medicines, the chance for side effects will be higher. If you experience a prolonged .