One of these is PAH. One of these is PAH. This, in turn, leads to more nitric oxide in the body. However, it stays in your body for up to 36 hours and can be taken every 24 hours, so it can work for you constantly. National Library of Medicine. The typicaldose of Viagra is 50 mg. Cialis and Viagra are equally effective. · For daily use of Cialis for ED, the usual starting dosage is mg per day. If this dosage isn’t effective for you, your doctor may increase your dosage to 5 mg per day. What is Cialis? Cialis is an ED treatment that works in 30 minutes and lasts for up to 36 hours (about 1 and a half days). It contains the active ingredient tadalafil and it’s effective for 80% of men. How to take Cialis. Take one tablet at least 30 minutes before sex. The effects of Cialis can last for up to 36 hours. How to save on generic Cialis There are many ways to save on Cialis, which is available as both a brand-name and generic medication. Save with GoodRx. GoodRx can help you save over 97% off the average retail price of the generic version. Generic Cialis at certain pharmacies is less than $13 with a free GoodRx discount.