Viagra vs. Cialis: A Detailed Comparison of Effectiveness & Ingredients

Question
Viagra takes one hour to be effective and lasts for about six hours (according to a Viagra brochure). The main ingredient in Viagra is Sildenafil. Cialis takes 30 minutes to be effective and lasts for about 36 hours (according to a Cialis brochure). The main ingredient in Cialis is Tadalafil. Why should Viagra take one hour to be effective and Cialis take 30 minutes to be effective? What is the difference between Sildenafil and Tadalafil? Thank you very much for your response. Al Brown

Answer
Both medications are in the same class, phosphodiesterase inhibitors.  So, they both basically do the same thing.  However, they are different medications.  They have different "half lives" which means the time it takes for the drug to be eliminated from the body.  The half life for Cialis is much longer than Viagra, so it stays in the body for a lot longer.  It is also absorbed through the stomach faster, so it's onset is quicker.

Hope this helps...