The National Institute for Health and Clinical Excellence (NICE) has published preliminary recommendations asking Bayer for more information on its oral anticoagulant Xarelto (rivaroxaban).

The Institute is seeking more information on the drug's use for the prevention of stroke and systemic embolism in people with atrial fibrillation (AF). These patients have about a five-fold greater risk of developing blood clots and subsequent stroke than people without AF because the erratic heart rhythm of AF causes turbulent blood flow within the heart chambers. However, the risk of stroke can be substantially reduced by appropriate use of antithrombotic therapy such as warfarin.

Xarelto has a UK marketing authorisation for the prevention of stroke and systemic embolism in patients with non-valvular atrial fibrillation who have one or more factors such as congestive heart failure, hypertension, age 75 years or older, diabetes mellitus, prior stroke or transient ischaemic attack (ITA).

Commenting on NICE's draft recommendation on the drug, Professor Carole Longson, director of the Institute's health technology evaluation centre, said that the importance of effective antithrombotic therapy in people with AF who are at risk of developing potentially fatal blood clots "cannot be overestimated."

Warfarin is the most commonly-used antithrombotic but it is associated with a number of problems such as the need for frequent monitoring of the blood's clotting, which can have an adverse effect on quality of life and makes compliance difficult for some people, she said.

Xarelto - like Boehinger Ingelheim's Pradaxa (dabigatran), which NICE is also assessing - represents a significant potential benefit for people with AF because it does not require regular monitoring and dose adjustments, said Prof Longson.

However, she added, NICE's independent appraisal committee has concluded that the population included in the single trial presented by the manufacturer as evidence of Xarelto's cost-effectiveness was not reflective of all the people with AF in the UK who might be eligible for treatment with the drug.

"In particular, the committee was concerned that the people in the warfarin arm of the trial, on average, did not achieve as good control of their blood clotting as might be expected in clinical practice in the UK. It was also concerned that the risk of stroke and systemic embolism for the population in the trial was higher than for the overall population eligible for treatment with [Xarelto]," said Prof Longson.

"The committee is therefore minded not to recommend the drug on the basis of the available evidence, pending the receipt of additional information from the manufacturer that will address these issues," she concluded.

NICE points out that it has not yet issued final guidance to the NHS, and that those wishing to comment on its draft recommendations have until January 30 to do so.