For this purpose, one dose works for up to 72 hours. How Quickly Does Cialis Work? The FDA has also approved tadalafil for treatment of both benign prostatic hypertrophy and erectile dysfunction where the two conditions co-exist. What Is Cialis? Ask your doctor if you are not sure whether any of your medications contain nitrates. Viagra is always taken as needed, usually about an hour before sex.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. Cialis Now Available as Generic Tadalafil: Here’s What You Need to Know – GoodRx We have good news for you: generic Cialis, used to treat erectile dysfunction . The recommended starting dose for Cialis intended for once daily use is mg, take at the same time each day, without regard to timing of sexual activity. This may be increased to 5mg/day based on need and tolerability. May be taken with or without food. Cialis is available as a generic, under the name tadalafil. 3.