It may not be safe to breastfeed while using this medicine. Tadalafil is in a class of medications called phosphodiesterase PDE inhibitors. If you are already taking medication to treat BPH, your doctor may tell you to stop taking your other medication at least one day before starting treatment with tadalafil. Tadalafil comes as a tablet to take by mouth. It may increase your risk of dizziness or fainting.Brand: Cialis. Form: oral tablet; Strengths: mg, 5 mg, 10 mg, and 20 mg; Adult dosage (ages 18–64 years) Tadalafil can be used either as needed or taken once a day. Don’t take.  · The typical dose for once-daily Cialis for ED is milligrams (mg) to 5 mg. When used as needed for ED, the usual Cialis dose is 10 mg (with a maximum daily dose of 20 mg). What is Cialis? 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).