Though, Pfizer lost a crucial patent protection on Lipitor and, with it, the exclusive right to make and sell the drug.

Competitors were ready to swoop in with generic versions and swoop out with many billions of dollars. In the next four years, patents on six other key Pfize medicines are due to expire.

Viagra, the drug of choice for treating erectile dysfunction, is another huge product for Pfizer.

The company went to court this summer to fight for control of it after a challenge from a generic manufacturer of Viagra. To the relief of Pfizer, a judge ruled that a key Viagra patent is valid until 2019.

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