If you need emergency medical care for a heart problem, it is important that your doctor knows when you last took tadalafil. If you experience a prolonged erection for more than 4 hours or a painful erection for more than 6 hours, contact your doctor immediately. People with kidney or liver problems will need to either take a lower dose of Cialis or avoid the medication altogether, depending on the severity of the condition. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Tadalafil is sometimes taken as needed, usually at least 30 minutes before sexual activity and not more often than once every 24 hours. It works best when taken one hour before sex. What does this mean?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.  · Cialis tablets come in four strengths: milligrams (mg), 5 mg, 10 mg, and 20 mg. What are the typical dosages of Cialis? Typically, your doctor will start you on a low dosage.  · Cialis tablets come in four strengths: milligrams (mg), 5 mg, 10 mg, and 20 mg. What are the typical dosages of Cialis? Typically, your doctor will start you on a low dosage.