Cialis can last in the system for up to 36 hours. Share personal information without ensuring the site is secure. This is a serious condition that requires immediate medical attention. John’s wort. These PDE5 inhibitors may cause headache, flushing, drop in blood pressure, or other adverse effects.Renal Impairment. 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 . Pros lasts up to 36 hours for some people, which is longer than Viagra can be taken as needed or on a daily, regular basis daily use allows for a more spontaneous . 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.