An erection results from an increase in blood flow to the penis. More serious side effects may include a drop in blood pressure or an erection that lasts longer than four hours. However, others work on a cash-pay basis and don’t partner with insurance companies. Most erectile dysfunction medications belong to the drug class known as PDE5 inhibitors , which help relax the muscles and increase blood flow to allow for a full erection. It’s best to check your chosen provider’s site for more information.Cialis is a popular ED medication. Find out everything you need to know about this doctor-prescribed medication including usage, effectiveness, and safety . What is Tadalafil (Cialis)? Drug Facts Common Brands Cialis Drug Class PDE-5 inhibitor Controlled Substance Classification Not a controlled medication Generic . • Cialis • Cialis • Adcirca, Alyq, and Tadliq: Form and strengths: • Oral tablet: mg, 5 mg, 10 mg, or 20 mg • Oral tablet: mg, 5 mg, 10 mg, or 20mg • Oral tablet: .