Summary Cialis and Viagra are both pills for treating erectile dysfunction. Tadalafil has been extensively studied for ED. What if I am taking other drugs? That means you can have erections whenever you want or need them. Which Lasts Longer? If you become pregnant while taking tadalafil, call your doctor.Cialis (tadalafil) is an orally administered prescription medication used for erectile dysfunction (ED) and pulmonary arterial hypertension (PAH) to reduce the . CIALIS is indicated for the treatment of ED and the signs and symptoms of BPH (ED/BPH). Limitation of Use If CIALIS is used with finasteride to initiate BPH treatment, such use is recommended for up to 26 weeks because the incremental benefit of CIALIS decreases from 4 weeks until 26 weeks, and the incremental benefit of CIALIS beyond. headache. indigestion. back pain. muscle pain. flushing. stuffy nose. Patients who get back pain and muscle aches usually get them 12 to 24 hours after taking Cialis and these usually go away by.