Brand names Why is this medication prescribed? Men with BPH usually have difficulty urinating, a decreased flow of urination, hesitation at the beginning of urination, and a need to get up at night to urinate. In BPH, the medication relaxes the urinary tract and bladder muscles, allowing for more effortless urine flow. Tadalafil is also sometimes taken once a day every day without regard to timing of sexual activity. If you are taking tadalafil to treat erectile dysfunction, you should know that it does not cure erectile dysfunction or increase sexual desire. If you drink a large amount of alcohol more than five glasses of wine or five shots of whiskey while you are taking tadalafil you are more likely to experience certain side effects of tadalafil such as dizziness, headache, fast heartbeat, and low blood pressure.Cialis lasts up to 36 hours in the body, while Viagra lasts 4–6 hours in the body. Both are taken 30 minutes before sex. Cialis can cause limb pain, while Viagra can cause vision change, rash. Brand-name Cialis: $ per month (5mg) Generic Cialis (tadalafil): starting at $40 per month (5mg, 10mg, 20mg) Daily generic Cialis (tadalafil): starting at . Cialis is a brand of tadalafil, one of the most popular medications to treat erectile dysfunction (ED).It was first approved in Cialis is popular because it offers dosing flexibility, works.