If you take nitrates in any form, or are on treatment for pulmonary hypertension , you should not take tadalafil. Tadalafil is not usually used to treat benign prostate enlargement because there is not enough evidence about how well it works. You should take tadalafil one time a day. Check the healthdirect’s medicines section for more information about tadalafil. Tadalafil does not prevent pregnancy or the spread of sexually transmitted diseases such as human immunodeficiency virus HIV. If you are thinking about using tadalafil please discuss it with your doctor.Tadalafil (Cialis) is used to treat erectile dysfunction (ED, impotence; inability to get or keep an erection), and the symptoms of benign prostatic hyperplasia (BPH; an enlarged prostate) which include difficulty urinating (hesitation, dribbling, weak stream, and incomplete bladder emptying), painful urination, and urinary frequency and urgency in adult men. headache. indigestion. back pain. muscle pain. flushing. stuffy nose. Patients who get back pain and muscle aches usually get them 12 to 24 hours after taking Cialis and these usually go away by. CIALIS for Use as Needed. Creatinine clearance 30 to 50 mL/min: A starting dose of 5 mg not more than once per day is recommended, and the maximum dose is 10 mg not more than once in every 48 hours. Creatinine clearance less than 30 mL/min or on hemodialysis: The maximum dose is 5 mg not more than once in every 72 hours [see .