You will still need to be sexually stimulated to be able to get an erection and maintain it. If you become pregnant while taking tadalafil, call your doctor. What special dietary instructions should I follow? Check the healthdirect’s medicines section for more information about tadalafil. Tell your doctor if any of these symptoms are severe or do not go away: headache.Cialis is a medication approved by the Food and Drug Administration (FDA) often used to treat erectile dysfunction (ED) and benign prostatic hyperplasia (BPH) in . 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. 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 .