Sexual activity may be a strain on your heart, especially if you have heart disease. Check the healthdirect’s medicines section for more information about tadalafil. Conclusion Navigating the vast ocean of medical treatments can be daunting. Your doctor may need to change the doses of your medications or monitor you carefully for side effects. Tell your doctor if any of these symptoms are severe or do not go away: headache. If you take nitrates in any form, or are on treatment for pulmonary hypertension , you should not take tadalafil.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. Yes, because tadalafil (Cialis) works by relaxing your blood vessels, it can lower your blood pressure. But your blood pressure shouldn’t drop by too much. In clinical studies, people who took the 20 mg dose of tadalafil (Cialis) experienced an average drop in blood pressure by about 2 mm Hg.  · But on average, its effects start to lessen 2 to 3 hours after you take a dose. The typical dose for once-daily Cialis for ED is milligrams (mg) to 5 mg. When used as needed for ED, the usual.