According to the German drug giant Bayer AG, the reason the company failed to inform U.S. regulators about a study on the risks of the heart-surgery drug Trasylol was a mistake.

Bayer apparently knew the controversial heart surgery drug was linked to dangerous side effects and death but say queries about the study methodology and the findings were preliminary.

This was, according to the company, six days before an FDA advisory panel met and ruled that Trasylol provided acceptable safety and effectiveness for preventing blood loss in certain patients undergoing heart bypass surgery.

Bayer only notified the FDA after it was asked to do so by the scientist conducting the study and now says it should have shared the information with the FDA prior to the September 21 advisory committee meeting, and this was a mistake on their part.

The FDA says the early findings from a new review of hospital records from 67,000 patients suggests that Trasylol use may increase the chances of death, serious kidney damage, congestive heart failure and strokes and it is now reviewing the data.

The FDA is now in the position of having to decide what changes need to be added to the current advice regarding Trasylol in cases where reducing blood loss during bypass surgery is essential.

The FDA sought the panel’s opinion after two other studies published in medical journals linked Trasylol use to kidney problems and one also said the drug could increase the chances of heart attacks and strokes.

The FDA says a new study which was commissioned by Bayer compared records from 30,000 patients treated with Trasylol to 37,000 treated with other products.

As with the earlier studies, the new research looked at patients who were not randomly assigned to receive various treatments which is an added complication when it comes to the assessment of whether Trasylol or other factors contributed to kidney or heart complications.

The FDA says the new report suggests that patients receiving Trasylol were at increased risk for death, kidney failure, congestive heart failure and stroke and they are evaluating this new data and the implications for appropriate use of the drug.

The FDA advises doctors to monitor Trasylol patients for signs of toxicity, particularly to the kidneys, heart or central nervous system.

Bayer too is said to be analyzing the preliminary findings as well as answers to questions it posed to the researcher who conducted the study.

The company has promised to work with the researcher and other experts “to examine the underlying source data and fully understand the results”.

Bayer’s mistake strengthens the case for public debate into improving drug safety in the U.S. by enhancing the FDA’s powers.

The Institute of Medicine has already called for the FDA to be given more power to prevent disasters such as the recall of the arthritis pill Vioxx by Merck two years ago.

Trasylol already carries a “black box” on its labeling, which warns doctors that it can cause kidney problems.