Cialis has been shown in clinical trials to stay in the body longer than the other selective enzyme inhibitors. It promotes erection within 30 minutes and enhances the ability to achieve erection for up to 36 hours.
Common side effects of selective enzyme inhibitors include headache, reddening of the face and neck (flushing), indigestion, and nasal congestion. Cialis may cause muscle aches and back pain, which usually resolve on their own within 48 hours.