Bayer has acknowledged that it failed to keep the US Food and Drug Administration informed of data that could have had a bearing on the outcome of an advisory panel meeting looking at the safety of Trasylol, used to prevent or reduce blood loss during surgery.

The preliminary findings from this new observational study of patients from a hospital database reported that use of Trasylol (aprotinin) may increase the chance for death, serious kidney damage, congestive heart failure and strokes.

Last month, the panel concluded that Bayer's Trasylol was safe and effective when used to prevent blood loss in patients undergoing coronary artery bypass grafting (CABG). But after seeing the new data, the FDA issued a warning that Trasylol should only be used only “where the clinical benefit of reduced blood loss is essential to medical management of the patient and outweighs the potential risks.”

It also said physicians who use Trasylol should carefully monitor patients for the occurrence of toxicity, particularly to the kidneys, heart, or brain, and promptly report observed adverse events.

Bayer said it "mistakenly did not inform the [FDA] about a retrospective study commissioned by the company to analyse the effects of aprotinin, aminocaproic acid and tranexamic acid in patients undergoing CABG surgery."

Data on Trasylol, "was not shared immediately with the agency because it was preliminary in nature and raised significant questions on the study population, outcomes and methodology," said the company.

The German firm has submitted a copy of the preliminary report to the FDA and has notified other regulatory authorities.

Trasylol sales were 75 million euros ($95 million) in the first half of 2006, though had dipped back 11% in the second quarter on the back of the safety concerns. Bayer has forecasted peak annual sales for the drug in the region of 500 million euros. Trasylol was first introduced in the USA in 2003.