Some of the company's biggest-selling products will be vulnerable to attack from generic equivalents this year - a so-called patent cliff puts annual sales worth more than 7.5bn at risk.

While they no longer have canon rules, they can be used as their generic equivalents.

The firm produced antibiotics, such as penicillin and tetracycline, waiting for the expiration of patents on brand-name medications and then producing generic equivalents at lower prices.