Antithrombotic Safety Linked to GFR

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Fondaparinux causes less bleeding than enoxaparin in some ACS patients with renal dysfunction

 

Fondaparinux may be safer than enoxaparin as treatment for non-ST-segment elevation acute coronary syndromes (ACS) in patients with renal dysfunction.

 

Keith A.A. Fox, MD, of the University of Edinburgh in the United Kingdom, and his colleagues based the finding on a subgroup analysis of 19,979 patients who participated in the Fifth Organization to Assess Strategies in Acute Ischemic Syndromes (OASIS 5) trial, a randomized, controlled study of patients with presenting with non-ST-segment elevation ACS.

 

The patients were divided into quartiles based on glomerular filtration rate (GFR): less than 58, at least 58 but less than 71, at least 71 but less than 86, and 86 mL/min per 1.73 m2 or higher.

 

Nine days after treatment, the composite end point of death, MI, or refractory ischemia occurred in 6.7% of fondaparinux recipients and 7.4% of those receiving enoxaparin, a nonsignificant difference between groups, the researchers reported in Annals of Internal Medicine (2007; 147:304-310). The researchers found no significant difference in treatment arms by GFR.

The rate of major bleeding events was significantly lower with fon-daparinux than enoxaparin at nine, 30, and 180 days after treatment across quartiles of renal dysfunction, with the difference most pronounced in patients with severe renal dysfunction.

 

Among subjects with a GFR below 58 mL/min per 1.73 m2, the rates of major bleeding events at

nine days in the fondaparinux and enoxaparin groups were 2.8% and 6.4%, respectively, which translated into a 58% lower risk of major bleeding in the fondaparinux recipients. At 30 days, the rates were 4.2% and 7.6%, respectively, for a 46% decreased risk among fondaparinux-treated subjects.

 

At 180 days, the rates were 5.8% and 8.7%, for a 35% lower risk of major bleeding in the fondaparinux group, researchers noted.

 

“A possible explanation for our findings is that clearance of enoxaparin may be impaired in patients with impaired renal function when the drug is administered in the standard dosing regimen, and this impaired clearance is clearly associated with excess bleeding,” the authors wrote. "Although the results of their analysis must be interpreted with caution, they noted, “these data suggest that the choice of therapy for non-ST-segment elevation ACS needs to take into account not only the effect on preventing ischemic events but also the effect on bleeding.”

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