The main reason behind its commercial success is its effect lasting up to 36 hours and comparatively lesser side effects reported using other brands. Though the initial rifts of management and controversies resulted in decline of its share prices but with the settling of the disputes between the aggrieved parties, in the next fiscal year it did covered up all the losses.

In the fiscal year 2004 Cialis had worldwide sales of up to $550 million and followed in by sales of $746 million in 2005 and again witnessing a sharp upsurge in 2006 of sales up to $971 million. A startling $1 billion in 2007 followed by a year marked with destabilization, economic crunch and recession though managed to muster good sales of $1.075 billion in 2008.

This shows that it has not only sustained but developed progressed and evolved as a trusted and reliable brand commercially and otherwise.

In 1991 then GlaxoWellcom (now Glaxo Smithklien) and Icos Corp under a partnership to develop new drugs discovered Tadalafil. As in 1993 Icos Corp began to study the compound IC351 and they were testing its usefulness and treatment for disorders. Later Icos Corp patented it in 1994 and in 1997 in clinical tests they found out its effectiveness for erectile dysfunction.

In 1998 Icos and Eli Lilly formed Lilly Icos Co for the development and commercialization of Tadalafil; as GlaxoWellcome let the agreement between Icos Corp and them lapse in 1996 as the drugs developed were not in their core markets.

Two years later in 2000 it was filed with United States Food and Drug Administration (FDA) for generic name Tadalafil and brand name Cialis. In 2003 FDA approved Tadalafil for the use of erectile dysfunction and in May 2009 has been recognized for the treatment for pulmonary arterial hypertension.