Bayer has revealed the findings of an independent lawyer’s investigation into the company’s failure to disclose data about the risks of Trasylol, used to reduce blood loss during heart surgery, which concludes that no cover-up was involved.

In October last year, Bayer 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 (aprotinin). Preliminary findings from this new observational study of patients from a hospital database reported that use of the drug may increase the chance for death, serious kidney damage, congestive heart failure and strokes.

A month earlier, the panel had 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.”

Bayer said at the time that 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." The aforementioned investigation was started by Fred Fielding but he was appointed chief White House counsel so William Taylor of Zuckerman Spaeder took over.

He has completed his report and says that the failure to supply the FDA with risk data for Trasylol “was not motivated by any intent to conceal the existence of the study but was regrettable human error". Bayer had said that the data was not shared immediately with the agency by two senior staff (since suspended) because it was preliminary in nature and Mr Taylor echoed this view.

He said “these two individuals did not immediately disclose this information, because they had significant questions about the study's methodology and analyses," noting that no other Bayer employees or any of the external consultants who supported the firm at the panel meeting knew that the preliminary report had been received.

Bayer added that it has undertaken “a thorough analysis” of all of the company’s drug safety and monitoring procedures and based on “Mr Taylor’s report, and lessons learned from this experience, we have strengthened a variety of already strong structures and rigorous processes”. In particular, the firm said it has made changes in the responsibilities of its protocol review committee, “a unit whose structured processes play a critical role in ensuring that the mistakes and omissions that occurred” are not repeated.

The drug was once predicted to be able to reach peak annual sales of more than 500 million euros but revenues in the second quarter fell 18.4% (though no sales figure was given), hurt by the FDA's insistence on a new label last year which highlights the possible risk of kidney damage associated with taking the drug, a claim disputed by Bayer.