The history of Cialis cannot be discussed without mentioning the drug of Pfizer, Viagra. The approval Of the FDA on March 27, 1998, carried out this drug of regulation, Viagra, with a success of inauguration per Juste the first year of the introduction like Pfizer sold the value of drugs above billion dollar. However, the things changed considerably for the giant of drugs érectiles of dysfunction when the FDA also approved Levitra on August 19, 2003, and of Cialis on November 21, 2003. In 1993 the company of Icos drug started to study IC351, which is an inhibitor of enzyme PDE5, and it is basically the process by which drugs érectiles of dysfunction function. In 1994, scientists of Pfizer have discovered this citrate of sildenafil, which is a white crystalline powder which standardizes temporarily the function érectile penis by blocking an enzyme known to prevent the production of a chemical which causes constructions, caused the patients of heart who took part in a clinical study of a medicine of heart to have constructions. Although the scientists did not examine chemical compound IC351 for the dysfunction érectile, the compound seemed to have a side effect which could potentially be worth the sorrow of the million, if not billion dollars. Soon Icos received its very first patent in 1994 on IC351, and the clinical tests of phase 1 took place in 1995. In 1997, to put 2 clinical studies started and Icos made a its first study on patients with the dysfunction érectile. Phase 2 lasted approximately two years, and then this phase 3 started.
 

At 1998, with ICOS Corporation, and Eli Lilly and Company, drug for the dysfunction érectile marketed, and two years after they classified a new application of drug with the administration of food and drug of the United States for IC351; the only difference was that this time they decided to call Cialis drug. In May of 2002, Icos and Eli Lilly and Company reported to American urologic association that the tests of phase 3 prove that Cialis functions during up to 36 hours, and a year after Icos and Eli Lilly and Company received the approval of the FDA of the United States for Cialis. An advantage that Cialis has finished Viagra is that the tadalafil has a half life 17.5 hours [2] (and thus Cialis is announced to work during up to 36 hours, even if it remains at this time approximately a quarter of the amount absorptive in the body) compared to 4 hours of half life for the sildenafil (Viagra). [3] [4]

Eli Lilly bought the company of ICOS for the dollars $2.1 billion in 2006.

Chemistry

The empirical formula for the tadalafil is C22H19N3O4, and its official organic name is (6R, 12aR) - 6 (1,3-benzodioxol-5-yl) - 2,3,6,7,12,12a- hexahydro-2-methyl-pyrazino [1, 2: ] pyrido 1.6 [3,4-b] indol-1,4-dione. The molecular weight is 389.41. The tablets of Tadalafil are yellow, film-coatings, and almond-formed, and are produced in 5, 10, or 20 magnesium amounts.

Mechanism of action

Tadalafil functions beside preventing PDE5, an enzyme found mainly in smooth fabric of muscle of arterial wall of the penis and the lungs. An amount of magnesium 20 of tadalafil is comparable with an amount of magnesium 100 of sildenafil (Viagra). [necessary quotation] by preventing PDE5, the tadalafil slackens blood vessels in the penis, the increasing flow of this fact of blood and to facilitate construction.

Part of the physiological process of construction implies the parasympathetic nervous system causing the outburst of nitric oxide (NO) in the cavernosum of corpus of the penis. AUCUNS seizings with the receivers of the cyclase of guanylate of enzymes which has like consequence the greatest levels of the cyclic monophosphate of guanosine (cGMP), driving to smooth the relieving of muscle (vasodilation) in the cavernosum of corpus, having for result the greatest contribution of blood and a construction.

Tadalafil is an effective and selective inhibitor of the specific type 5 (PDE5) of phosphodiestérase of cGMP which is responsible for the degradation of the cGMP in the cavernosum of corpus. The molecular structure of the tadalafil is similar to that of the cGMP and acts as a competing binder of PDE5 in the cavernosum of corpus, having for result more cGMP and better constructions. Without sexual stimulation, and thus lack of activation of the system of NO/cGMP, the tadalafil should not cause a construction. Other drugs which function by the same mechanism include the sildenafil (Viagra®) and the vardenafil (Levitra®).