Regulators in the USA have rejected a bid by AstraZeneca to delay the entry of generic versions of its antipsychotic blockbuster Seroquel.

The Anglo-Swedish drugmaker has revealed that the US Food and Drug Administration had denied Citizen Petitions requesting that the agency withhold finally approving any generic with labelling that omits warnings  required for branded versions of Seroquel (quetiapine) and Seroquel XR. Those warnings relate to hyperglycaemia.

AstraZeneca said it is "evaluating the FDA’s decision and reasoning". The patent on Seroquel, which has paediatric exclusivity, is set to expire on March 26. As for Seroquel XR, AstraZeneca reached a settlement with the USA's Handa Pharmaceuticals in September which prevents the latter from selling a generic form until the end of 2016.