Tadalafil increases blood flow to particular areas of the body and is used to treat erectile dysfunction. Learn about side effects, interactions and indications. Find drug information for Tadalafil on CVS.com, including related drug classes, side effects, dosage, and answers to frequently asked questions. Tadalafil 20 mg is the maximum as-needed dose for ED. Learn about its uses, how long it lasts, side effects, and how to save on your prescription. Find drug information for Tadalafil on CVS.com, including related drug classes, side effects, dosage, and answers to frequently asked questions. For ED, Tadalafil can be taken either once per day or as needed before sexual activity, with dosages ranging from 2.5 milligrams (mg) to 20 mg. In the study of 10 mg tadalafil for 6 months and the study of 20 mg tadalafil for 9 months, results showed a decrease in mean sperm concentrations relative to placebo, although these differences were not clinically meaningful. Tadalafil is used to treat men who have erectile dysfunction (also called sexual impotence). Tadalafil belongs to a group of medicines called phosphodiesterase 5 (PDE5) inhibitors. Tadalafil is used to treat male sexual function problems (impotence or erectile dysfunction-ED). In combination with sexual stimulation, tadalafil works by increasing blood flow to the penis to help a man get and keep an erection. Tadalafil (Eqv-Cialis) is used in adult men to treat erectile dysfunction (impotence) and symptoms of benign prostatic hypertrophy (enlarged prostate). Tadalafil (Eqv-Cialis) can also be used in men and women to treat pulmonary arterial hypertension (PAH) and improve exercise capacity. Tadalafil belongs to a group of medicines, known as phosphodiesterase-5 (PDE-5) inhibitors, which are used to treat erectile dysfunction or pulmonary arterial hypertension.