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The History Of Cialis: An Accidental Invention!

FDA_tadafil

Cialis (Tadalafil) received US Federal Drug Administration (FDA) approval for commercial sale on November 21, 2003. But the “real” history of the drug commences way back – in 1994 – following the “accidental” discovery of the potential of another drug – Sildenafil – also a phosphodiesterase type 5 (PDE5) enzyme inhibitor, just like Tadalafil!

The world of discovering miraculous drugs is filled with accidents. And just as Sir Alexander Fleming accidentally discovered Penicillin in 1928, it was an “accident” that lead to the discovery of Cialis, too.

In 1994, scientists from the drug giant Pfizer were conducting drug trials for a heart medication known as Tadalafil. The hope was that it would be a much needed breakthrough drug that could be used in the treatment of a number of pulmonary conditions. However, during human trials of the drug, male volunteers using Tadalafil reported unusual symptoms to the researchers: they (the male test subjects) got unexplained erections when on the drug.

pfizer-pillsWhen Pfizer informed the world about the capabilities of Tadalafil, its PDE5 inhibiting drug (which would later be marketed as Viagra), the scientists at ICOS Corporation took note. They were working on a PDE5 inhibitor of their own, patented as compound IC351, in partnership with the drug giant Glaxo Welcome way back in 1991. The 1994 “accidental discovery” of Tadalafil shed new light on the abilities of compound IC351, and ICOS researchers started looking closely at their own drug.

By 1998, ICOS was no longer a Glaxo partner, so it formed a joint venture with Eli Lilly Company (Lilly ICOS, LLC) to further explore and develop IC315. In May 2002, the new company was able to disclose to the world that its new PDE5 inhibitor Tadalafil (which it would market under the brand Cialis), had a half-life of 17.5 hours, compared to Sildenafil’s meager 4-hour half-life! This meant that Cialis would work for up to 36 hours for men that took it.

A year after making this dramatic announcement to the American Urological Association (AUA), in 2003, Cialis (Tadalafil) received FDA approval for treatment of Erectile Dysfunction (ED), and was now in direct competition with Pfizer’s ED drug Viagra (Sildenafil).

But ED is not the only condition that Cialis (Tadalafil) is prescribed to treat. The FDA also approved Cialis for treating Benign Prostatic Hyperplasia (BPH) in 2011, as well as for treating men exhibiting a combination of ED and BHP symptoms. This came after the manufacturers successfully received FDA approval in May 2009 for the use of Tadalafil, sold under the brand name Adcirca, in treating Pulmonary Arterial Hypertension (PAH).

As can be seen, the history of Tadalafil, this multi-faceted drug that is used for treatment of multiple conditions, RD, BPH and PAH, has its beginning in the accidental discovery of a totally unrelated drug.