Generic Cialis is used to treat male impotence also referred to as erectile dysfunction (ED). Generic Cialis has the same active ingredient as brand name Cialis, and is equivalent in effect, strength, and dosage. This bestselling pill offers the longest performance period on the market. When taken 15 minutes before intercourse it can last up to 36 hours. The success rate of oral ED drugs is very high, above 90%. However different people require different dosages to attain optimum results.