This medicine is also used to treat erectile dysfunction and signs and symptoms of BPH. Tadalafil is also used to treat men who have signs and symptoms of benign prostatic hyperplasia BPH. The typicaldose of Viagra is 50 mg. If you are a Mayo Clinic patient, this could include protected health information. Comparison with actions of other PDE5 inhibitors[ edit ] Sildenafil and vardenafil inhibit PDE6, an enzyme found in the eye, more than tadalafil. If you are taking tadalafil for erectile dysfunction, your doctor will probably start you on an average dose of tadalafil and increase or decrease your dose depending on your response to the medication. This increased blood flow can cause an erection.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 . It is the brand name for tadalafil, a medication also used to treat ED. Tadalafil is in a class of drugs called phosphodiesterase-5 (PDE5) inhibitors and is available in a generic form . Cialis contains the active drug ingredient tadalafil and belongs to a group of medications called phosphodiesterase 5 (PDE5) inhibitors. For ED, Cialis relaxes the blood vessels .