Standard or extended-duration prophylaxis in medical patients? A review of the evidence

Acutely ill medical patients are at significant risk of venous thromboembolism (VTE). Thromboprophylaxis can substantially reduce the incidence of VTE, but to be optimally effective must consist of the correct choice of agent, at an appropriate dose, and for sufficient duration. Increasing evidence suggests that VTE risk persists beyond the standard period of prophylaxis. Although there is evidence that extended-duration prophylaxis is beneficial in preventing late VTE complications in high-risk surgical patients, few data exist in medical patients. The recent EXCLAIM study demonstrated that, subsequent to a standard prophylaxis regimen of 10 ± 4 days with enoxaparin 40 mg once daily, extended-duration prophylaxis (28 ± 4 days) with enoxaparin reduced total VTE events compared with placebo: 2.5% versus 4.0%; (absolute risk difference -1.53%; 95.8% confidence interval [CI] -2.54 to -0.52), with parallel increases in major bleeding rates (0.8% vs. 0.3%; absolute risk difference 0.51%; 95% CI 0.12-0.89%). The reduction in total VTE was principally driven by a decrease in symptomatic deep-vein thrombosis (absolute risk difference -0.60%; 95.8% CI -1.00 to -0.19%). Favorable benefit-to-risk ratios were observed in certain high-risk patient groups: level 1 immobility, women, and age >75 years. In addition to their underlying medical condition, medical patients often have multiple risk factors, placing them at sustained risk of VTE. Extended-duration prophylaxis might be most relevant in such patients. The development of appropriate risk assessment tools could help identify medical patients at greatest risk of late VTE events who might benefit most from extended-duration prophylaxis.