More serious side effects may include a drop in blood pressure or an erection that lasts longer than four hours. Cialis tadalafil : This ED medication works with the same principle as Viagra, but lasts up to 36 hours. Here are some key factors to consider when deciding: Pricing: Know how much your monthly supply will cost with shipping and tax. You’ll also need to fill out a medical questionnaire with answers about your medical history, current medications, and lifestyle habits. Compare your options before enrolling to find the plan that meets your specific needs. Other warning signs of an unsafe online pharmacy include outdated medication, no customer service, or suspiciously low prices.What is Tadalafil (Cialis)? Drug Facts. Common Brands Cialis. Drug Class PDE-5 inhibitor. Controlled Substance Classification Not a controlled medication. . Introduction. If you’re looking at treatment options for erectile dysfunction (ED), you may want to learn more about Cialis and its cost. It’s a prescription drug used . Our medical team can prescribe it online and our pharmacy can mail it to you in 5mg, 10mg and 20mg dose. An even lower cost option for ED medicines is generic sildenafil 20mg .