Shares have fallen by 4 percent at AstraZeneca after the drug giant posted a fall in sales.

Sales dropped in the last three months by 16 percent from a combination of expired drug patents, few new drug releases and rising operating costs.

"Our performance in 2012 reflects a period of significant patent expiry and tough market conditions globally", said CEO, Pascal Soriot said in a statement.

The company has predicted that 2013 will see reduced earnings as operating costs are predicted to continue to rise.