Because they are the same class of medications, they have similar side effects and effectiveness. The most common side effects are headaches, feeling sick, indigestion and facial flushes. Daily doses are often between 2. Both Cialis and Viagra work quickly. There is also the option to take Cialis as needed. Talk with your healthcare provider about your sex life and desired use.Patients should not use CIALIS if sex is inadvisable due to cardiovascular status ().Use of CIALIS with alpha-blockers, antihypertensives or substantial amounts of alcohol (≥5 units) may lead to hypotension (, ).CIALIS is not recommended in combination with alpha-blockers for the treatment of BPH because efficacy of the . The maximum dose is 10 mg not more than once in every 48 hours. CrCl less than 30 mL/min or on hemodialysis: The maximum dose is 5 mg orally once every 72 hours. Once a day use for ED: CrCl 30 mL/min or greater: Data not available. CrCl less than 30 mL/min or on hemodialysis: Not recommended. Once a day use for BPH. Dosage. The dose of Cialis you need will depend on whether you’re taking it daily or as needed. Daily doses are often between and 5 milligrams (mg). The as-needed dose is usually 10 mg but can range from 5–20 mg. The typicaldose of Viagra is 50 mg. However, the dosage can range from 25– mg.