Eli Lilly who manufacture the erectile dysfunction medication Cialis have posted increased sales for the drug in the second financial quarter.

At the same time Pfizer who make the erectile dysfunction drug Viagra have reported slightly reduced sales for the world's No.1 impotence medication compared to Cialis.

When Viagra first came on to the market over ten years ago it obviously had 100 percent market share as there were no rivals. With the arrival however of Cialis Viagra has consistently been losing market share but nevertheless continues to maintain the largest market share in most countries around the world.

What is so fascinating however about Cialis is that it is so different from Viagra in that instead of working for just a four hour time window, the drug can be effective for as long as 36 hours. Doctors and erectile dysfunction specialists say that this is the reason why it has consistently taken market share from Pfizer's Viagra.

The other erectile dysfunction drug Levitra has never really had any serious impact on the sales of the Viagra because it is basically extremely similar. In testing done comparing Viagra to Levitra there were no significant differences reported by the men using them. Some men said they preferred the Viagra and some men said they preferred the Levitra. Viagra has a big advantage in that its brand is so well known that men feel safer asking for it than asking for something which is relatively unknown.

The reality is the effectiveness of the three drugs Viagra, Cialis and Levitra are statistically identical and in any case they all function in exactly the same way by being PDE-5 inhibitors.

Cialis however continues to gain the advantage on Viagra and Levitra because of the fact that it works for such along time.

This means that a man who is planning a romantic weekend away does not need to fumble with his Viagra just before sex but can just take Cialis at the beginning of the weekend and feel confident that his erectile function will be good when he needs it.

It is likely that Cialis will continue to steal market share from Viagra over the next few years.

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