According to the FDA, generic medications contain the same active ingredients as brand names, meaning there’s no difference in effectiveness or safety. Read our editorial process. What special precautions should I follow? What special dietary instructions should I follow? The FDA has also approved tadalafil for treatment of both benign prostatic hypertrophy and erectile dysfunction where the two conditions co-exist. How long does Cialis last?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. Oral medications, like Viagra and Cialis, which require a prescription and are commonly used to treat ED, can take 30 minutes to take effect, she adds. Injections take less time to work, but they. Viagra is only available with a prescription in the United States, Canada, and most other countries. Viagra is sold under the generic name sildenafil, which is also .