Two boxes with the new anti-impotence drug Cialis (tadafil) are pictured in a Munich pharmacy February 4, 2003. Cialis has gone on sale in several European markets this week, spelling the end of Viagra's five-year market monopoly. The company Eli Lilly is hoping to cash in on the market that helped propel sales of Viagra, which launched five years ago, to more than $2.83 billion.