Tadalafil may cause side effects. If you experience chest pain, dizziness, or nausea during sexual activity, call your doctor immediately or get emergency medical treatment, and avoid sexual activity until your doctor tells you otherwise. Without physical action to the penis, such as that occurring during sexual intercourse, tadalafil will not work to cause an erection. Alternatively, Cialis may be prescribed as an as-needed treatment for ED, to be taken before sexual activity. John’s wort.Cialis is used to treat erectile dysfunction (impotence) and symptoms of benign prostatic hypertrophy (enlarged prostate). Another brand of tadalafil is Adcirca, which is used to treat pulmonary arterial hypertension . 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 those assigned male at birth. In combination with sexual stimulation, tadalafil works by increasing blood flow to the penis to help a man get and keep an test1.rufil is also used to treat the symptoms of an enlarged.