AstraZeneca, the Anglo-Swedish pharmaceutical group, is poised to pay more than $500m (£302m) to settle allegations in the US of marketing abuses of its second-most important drug.

In a trading update that showed third-quarter results had been boosted by flu vaccine sales, the company said it had reached “an agreement in principle” with the US Department of Justice to implement reforms and settle civil claims with an increased provision of $520m.