Pfizer Inc's patent on Norvasc, a hypertension drug, was invalidated by the U.S. Court of Appeals for the Federal Circuit in Washington based on the drug's key ingredient.

Bloomberg News reports:

Because the drug is an "obvious" variation of earlier inventions, the patent is invalid. Pfizer said it may appeal the decision.

Norvasc is Pfizer's second-biggest selling drug, and its patent expires in September. Mylan L  More ...