Cialis is a brand-name prescription medication. Your doctor will help you decide the best time for you to take tadalafil before sexual activity. Your doctor may need to change the doses of your medications or monitor you carefully for side effects. Cialis was also investigated in combination with finasteride, another BPH medication, in another trial. Obesity Additionally, certain risk factors increase the risk of ED, such as smoking , lack of exercise, and drug or alcohol use.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. CIALIS for once daily use: ED: mg taken once daily, without regard to timing of sexual activity. May increase to 5 mg based upon efficacy and tolerability. BPH: 5 mg, taken at approximately the same time every day ED and BPH: 5 mg, taken at approximately the same time every day (, ). Tadalafil (Cialis) is a phosphodiesterase-5 enzyme (PDE-5) inhibitor. It works by blocking PDE This is a protein in your body that breaks down the molecules that normally cause an erection. When it blocks PDE-5, tadalafil (Cialis) helps an erection occur by allowing certain muscles in the penis to relax and the penis to fill with blood.