Tadalafil is sometimes taken as needed, usually at least 30 minutes before sexual activity and not more often than once every 24 hours. Even if your prescription drug plan covers Cialis, you may have to pay a higher percentage of the cost because Medicare categorizes Cialis as a non-preferred brand-name, or specialty drug a tier 3 drug. Tadalafil may cause side effects. Washington, S. These prices can also vary depending on where you purchase the medication, your insurance and several other factors. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand.Tadalafil (Cialis) is used to treat erectile dysfunction (ED, impotence; inability to get or keep an erection), and the symptoms of benign prostatic hyperplasia (BPH; an enlarged . Published on October 18, warning This article is no longer being updated and some information may not be current. Visit the GoodRx Healthhomepage for our latest articles. . Tadalafil is in a class of drugs called phosphodiesterase-5 (PDE5) inhibitors and is available in a generic form often called generic Cialis. Tadalafil has been on the .