First there was Viagra and Levitra.  Then came Cialis, the third erectile dysfunction drug approved by the Food and Drug Administration on November 21, 2003. FDA’s approval of Cialis was only three months behind Levitra which was approved on August 19, 2003.

Pfizer’s Viagra has monopolized the market for people with erection problems for over five years and the approval of the two drugs is expected to provide Viagra a worthy competition.

ICOS, the Washington-based company behind Cialis, started researching on IC351 which is a PDE5 enzyme inhibiter as early as 1993 and got its patent in 1994.  Just like Viagra, the preliminary studies behind Cialis were not targeted at discovering an erectile dysfunction drug.  ICOS only started studying the effects of IC351 on patients with erectile dysfunction in 1997.

The joint venture between ICOS and Eli Lilly in 1998 paved the way for the commercialization of the drug which led to the new application with the FDA and the renaming of the drug from IC451 to Cialis.  Cialis was first approved in Europe in November 2002 as an erectile dysfunction drug before it was approved by the US FDA for the same purpose.

With Eli Lilly’s purchase of ICOS Corporation in 2006 (but acquisition negotiations were completed only in January 2007), it became the sole manufacturer of Cialis.  Eli Lilly is a Fortune 500 corporation base din Indianapolis in the United States.  With no less than $14.5 billion revenue in 2006, it is considered the 148^th largest company in the United States and is publicly traded in the New York Stock Exchange,

While Viagra already had a foothold in the market due to its approval five years earlier, Tadalafil which is being sold under the brand name Cialis was able to get its own market share due to its 36-hour efficacy compared to Viagra’s 4-hour efficacy.  Due to its longer efficacy, Cialis has often been referred to as the weekend drug.

Cialis is also being marketed as a stronger drug than Viagra with a 100 mg of Viagra comparable to only 20 mg of Cialis.  This is the reason why Cialis is being prescribed at a lower dose beginning at 10 mg.  However, the dose can be increased or decreased depending on individual circumstances.

Despite this advantage, Cialis has invested a lot for its marketing and advertisement.  It was one of the halftime advertisers during the 2004 Super Bowl.

Not satisfied with being Viagra’s competitor as an erectile dysfunction medicine, Cialis is also undergoing further tests for possible use as a once a day therapy for pulmonary arterial hypertension.  Pfizer’s Sildenafil or Revatio is presently being sold as a 3-times day medication for pulmonary arterial hypertension.