Just a month after it was deemed okay to remain on the market, Bayer’s controversial Trasylol is once again being evaluated by US regulators amid renewed fears about its safety profile.

The US Food and Drug Administration says it is going to re-evaluate Trasylol (aprotinin), which is used to reduce blood loss during heart surgery, after being notified of a data safety monitoring board’s recommendation to stop patient enrolment in a planned 3,000-patient BART study. Preliminary findings suggest that Trasylol increases the risk of death compared to two antifibrinolytic drugs used in the study, epsilon-aminocaproic acid and tranexamic acid.

The FDA did note that the use of aprotinin was associated with less serious bleeding than either of the comparator drugs but more deaths due to haemorrhage had been observed among patients receiving Trasylol. As a result, the agency will re-evaluate the overall risks and benefits of the Bayer drug and this process “may result in the need to revise the labelling or other regulatory actions”.

Bayer responded by saying that it has issued new guidance to physicians and healthcare providers regarding the use of Trasylol, adding that the data will now be collected from all its trial centres throughout Canada and analysed by those conducting the BART study. However this process “is expected to take between four and eight weeks”, the company said, so “no further evaluation either by Bayer or by regulatory authorities can take place until additional information becomes available from the BART investigators”.

The Leverkusen-headquartered firm said that it believes Trasylol “remains a safe and effective treatment option for physicians” but it will continue to work closely “with medical experts, the FDA and health authorities in countries where Trasylol is marketed to re-evaluate the overall risk-benefit of the product”.

Bayer has had a troubled time with Trasylol of late. In August, it revealed the findings of an independent lawyer’s investigation into the company’s failure to disclose data about the risks of Trasylol, which concluded that no cover-up was involved. In October last year, Bayer acknowledged that it failed to keep the FDA informed of data that could have had a bearing on the outcome of an advisory panel meeting looking at the safety of Trasylol.

This was followed in December 2006 by yet another FDA review which changed the label on the drug to highlight the possible risk of kidney damage associated with taking it. However in September the agency’s Cardiovascular and Renal Drugs and the Drug Safety and Risk Management Advisory Committees voted 15 to one to keep Trasylol on the market, despite the potential health risks.