Tadalafil is sometimes taken as needed, usually at least 30 minutes before sexual activity and not more often than once every 24 hours. If you are taking tadalafil to treat erectile dysfunction, follow your doctor’s directions and the guidelines in this paragraph. Tadalafil is in a class of medications called phosphodiesterase PDE inhibitors. Take tadalafil exactly as directed. Furthermore, the longer half-life is the basis for tadalafil’s daily therapeutic use in treating pulmonary arterial hypertension. This combination can cause dangerously low blood pressure. If you’re not sure if you’re taking a nitrate, ask your doctor or pharmacist.Form: oral tablet. Strengths: milligrams (mg), 5 mg, 10 mg, and 20 mg. In this article, you’ll find additional information about Cialis’s dosage and details on how to take the drug. For a comprehensive overview of Cialis, view this article. Cialis is taken as an oral tablet, either as a low dose daily medication or as a higher-dose “on-demand” medication. It is the brand name for tadalafil, a medication also used to treat ED. About tadalafil Brand names: Cialis, Adcirca. About tadalafil. Tadalafil is a medicine used to treat erection problems (erectile dysfunction) and symptoms of an enlarged prostate (benign prostate enlargement). It’s also sometimes used to treat pulmonary hypertension (high blood pressure in the blood vessels that supply the lungs).