The activated clotting time (ACT) may not be a reliable methodto monitor heparin therapy when aprotinin is used concurrently.This is because aprotinin increases ACT monitored by somemethods, without actually increasing anticoagulation.
Clinical evidence,mechanism, importance and management
Aprotinin prolongs activated clotting time (ACT) as measured by a celite surface activation method, although kaolin ACT is much less affected (See reference number 1). Therefore, if ACT is used to monitor effectiveness of heparin anticoagulation during cardiopulmonary bypass incorporating aprotinin, this may lead to an overestimation of degree of anticoagulation. This may result in patients not receiving additional necessary heparin during extended extracorporeal circulation, or receiving excess protamine to reverse effects of heparin at end of procedure. The UK manufacturer of aprotinin notes that it is not necessary to adjust usual heparin/protamine regimen used in cardiopulmonary bypass procedures when aprotinin is also used (See reference number 2). The US manufacturer provides additional detailed information on appropriate methods to monitor heparin anticoagulation in presence of aprotinin (See reference number 1).
Trasylol (Aprotinin). Bayer HealthCare. US Prescribing information,December 2003.
Trasylol (Aprotinin). Bayer plc. UK Summary of product characteristics,September 2006.