Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine. Tadalafil stops the breakdown of a chemical responsible for relaxing muscles. This increased blood flow can cause an erection. Tadalafil is also used to treat men who have signs and symptoms of benign prostatic hyperplasia BPH. Do not use more of it, do not use it more often, and do not use it for a longer time than your doctor ordered.Cialis (tadalafil) is an orally administered prescription medication used for erectile dysfunction (ED) and pulmonary arterial hypertension (PAH) to reduce the symptoms of an enlarged prostate. 20 mg, 40 mg • Oral suspension: 20 mg per 5 mL: Typical dosage: • As needed dosing: 5–20 mg prior to sexual activity • Daily: –5 mg.  · Cialis tablets come in four strengths: milligrams (mg), 5 mg, 10 mg, and 20 mg. What are the typical dosages of Cialis? Typically, your doctor will start you on a low dosage. Then. Tadalafil is available in several doses in tablet form: milligrams (mg), 5 mg, 10 mg, and 20 mg. Depending on the dose for ED, you can use it as needed before sexual activity, or take it once.