The medication should be taken once daily at about the same time every day to maintain a consistent level of medicine in the body. Cialis stays in your system for up to 36 hours and may provide support for erections during that entire time. Tadalafil may cause side effects. When the blood vessel muscle cells relax, this expands the vessel and increases blood flow; this effect is referred to as vasodilation. However, everyone is different, and it may take less time or more time to work for you. Both medications are generic now and can be found at discounted rates, making them more accessible to the public than ever before.Use this coupon to get this price at any WALGREENS Pharmacy location. Expand to see all locations within your area. 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. Tadalafil (Cialis) is available both as brand-name and generic tablets. Common side effects of this medication include headache and indigestion. Tadalafil .