Some studies show that Cialis reaches its maximum effect around two hours after taking an as-needed dose. This is important for your overall health and safety, as certain medications can negatively interact with each other or cause existing conditions to worsen. Cialis tadalafil : This ED medication works with the same principle as Viagra, but lasts up to 36 hours. It was initially studied for use in hypertension high blood pressure and angina pectoris a symptom of ischaemic heart disease. It is thought that this reduced sales over the Internet and was safer as males could be referred for medical advice if appropriate. A dose of Cialis can remain effective in the body 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. Price and dosage: Brand-name Cialis: $ per month (5mg) Generic Cialis (tadalafil): starting at $40 per month (5mg, 10mg, 20mg) Daily generic Cialis (tadalafil): starting at $40 per month (mg. It is available in generic and brand versions. Generic sildenafil is covered by most Medicare and insurance plans, but some pharmacy coupons or cash prices may be lower. Get sildenafil for as low as $, which is 95% off the average retail price of $ for the most common version, by using a GoodRx coupon.