Because Tadalafil is a phosphodiesterase type 5 inhibitor and prescription-only, it cannot be bought over the counter. What you pay depends on the dose and quantity your provider recommends. Cialis relaxes muscles of the blood vessels and increases blood flow to particular areas of the body. Cialis is used to treat erectile dysfunction (impotence) and symptoms of benign prostatic hypertrophy (enlarged prostate). Cialis is a brand-name oral tablet that’s prescribed for erectile dysfunction (ED) and benign prostatic hyperplasia (BPH). Cialis contains the active ingredient tadalafil. Cialis (tadalafil) is a prescription medication that treats erectile dysfunction by improving blood flow to the penis. Cialis (tadalafil) is a prescription tablet used for erectile dysfunction and benign prostate hyperplasia. Learn about alternatives, dosage, side effects, and more. Cialis (tadalafil) is a prescription medication for erectile dysfunction (ED). If you take Cialis as needed, it usually starts working within 30 minutes but can take up to 2 hours to fully set in. Cialis is the brand name for tadalafil, a medication used to treat ED. It belongs to group of drugs called phosphodiesterase-5 (PDE5) inhibitors. Tadalafil relaxes muscles of the blood vessels and increases blood flow to particular areas of the body. Tadalafil under the name of Cialis is used to treat erectile dysfunction (impotence) and symptoms of benign prostatic hypertrophy (enlarged prostate). Cialis is a brand name for the drug tadalafil, which belongs to a drug class called phosphodiesterase inhibitors (PDE5 inhibitors). Phosphodiesterase type 5 is an enzyme that controls blood flow in blood vessels around the penis, lungs, and other areas. Tadalafil – better known by its brand name Cialis – is one of the most commonly prescribed drugs for erectile dysfunction.