viagra online

A lot of men suffer from erectile dysfunction, that’s why there is brisk demand for drugs that treat ED. Among then well known Viagra, Cialis, Levitra, Kamagra and so on. The first drug appeared on market was Viagra in 1998. Viagra was made by Pfizer and in 2002 its sales amounted to only $1.4 billion. A great success of Viagra did not stop other drugmakers from trying to get onto the market. And as a result Bayer and GlaxoSmithKline have launched their Levitra, a similar drug as Viagra. Cialis became a first true competitor of Viagra. First of all, there should be mentioned that the sell market of Cialis has reached an enormous level which is bound to put aside the success registered by Viagra in the late 90’s. The main advantage of cialis over Viagra is that it has more rapid effects than Viagra, it starts to work at approximately sixteen minutes after taking the pill, while the entire process can lead up to twenty four hours or more.