Elderly Medical Patients Treated with Prophylactic Dosages of Enoxaparin

The safety and optimal use of prophylactic treatment with low-molecular-weight heparins in elderly patients with impaired renal function remain undefined.

The primary aim of this study was to analyse, in ‘real life’, the influence of renal function, as assessed by Creatinine clearance (CLcr), on the level of anti-Xa activity in medical hospitalised elderly patients receiving prophylactic dosages of enoxaparin. Consecutive hospitalised acutely ill medical patients aged ≥75 years receiving daily dosages of enoxaparin 4000IU for up to 10 days were prospectively enrolled in two centres. Peak anti-Xa activity was measured at the beginning and during the course of therapy.

One hundred and twenty-five patients (31 men, 94 women), mean age 87.5 ± 6.3 years, mean bodyweight 56.4±11.9kg and mean CLcr 39.8 ± 16.1 mL/min, were enrolled in the study. The mean maximum anti-Xa activity (day 1 to day 10) [anti-Xa_maxl–l0] was 0.64 ± 0.23 IU/mL (range 0.24–1.50 IU/mL). Weak negative correlations were found between CLcr and anti-Xa_max and between bodyweight and anti-Xa_max. Mean anti-Xa_max was slightly but significantly higher in patients with CLcr of 20–30 mL/min compared with patients with CLcr of 31–40,41–50 or 51–80 mL/min (0.72 versus 0.61, 0.61 and 0.60 IU/ mL, respectively), and in patients weighing <50kg compared with patients weighing 50–60kg or >60kg (0.74 vs 0.64 and 0.52 IU/mL, respectively). Serious bleeding occurred in five patients, but anti-Xa_max values in these patients were not different to those in patients without bleeding (p = 0.77). Individual anti-Xa_max at the beginning or during the course of treatment was measured in the subgroup of 58 patients in whom anti-Xa activity was measured at least once during the study. The mean anti-Xa_max value was slightly but significantly higher during the course of the therapy than at the beginning of the study (0.63 ± 0.26 IU/mL vs 0.56±0.23 IU/mL, p = 0.012).

Only CLcr <30 mL/min and bodyweight <50kg were associated with significantly higher anti-Xa_max values. The clinical relevance of these increases remains questionable. No conclusions about the safety of enoxaparin in elderly medical patients can be drawn from these findings.