title: Elderly medical patients treated with prophylactic dosages of enoxaparin: influence of renal function on anti-Xa activity level.
abstract: BACKGROUND
  The safety and optimal use of prophylactic treatment with low-molecular-weight heparins in elderly patients with impaired renal function remain undefined.
  
  
  METHODS
  The primary aim of this study was to analyse, in 'real life', the influence of renal function, as assessed by creatinine clearance (CL(CR)), on the level of anti-Xa activity in medical hospitalised elderly patients receiving prophylactic dosages of enoxaparin. Consecutive hospitalised acutely ill medical patients aged >or=75 years receiving daily dosages of enoxaparin 4000 IU 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.
  
  
  RESULTS
  One hundred and twenty-five patients (31 men, 94 women), mean age 87.5 +/- 6.3 years, mean bodyweight 56.4 +/- 11.9 kg and mean CL(CR) 39.8 +/- 16.1 mL/min, were enrolled in the study. The mean maximum anti-Xa activity (day 1 to day 10) [anti-Xa(max1-10)] was 0.64 +/- 0.23 IU/mL (range 0.24-1.50 IU/mL). Weak negative correlations were found between CL(CR) and anti-Xa(max) and between bodyweight and anti-Xa(max). Mean anti-Xa(max) was slightly but significantly higher in patients with CL(CR) of 20-30 mL/min compared with patients with CL(CR) 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 <50 kg compared with patients weighing 50-60 kg or >60 kg (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).
  
  
  CONCLUSIONS
  Only CL(CR) <30 mL/min and bodyweight <50 kg 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.
authors.affiliation: Internal Medicine Department A, Lariboisière Hospital, Paris, France. isabelle.mahe@lrb.aphp.fr
authors.forename: Isabelle
authors.initials: I
authors.lastname: Mahe
authors.forename: Isabelle
authors.initials: I
authors.lastname: Gouin-Thibault
authors.forename: Ludovic
authors.initials: L
authors.lastname: Drouet
authors.forename: Guy
authors.initials: G
authors.lastname: Simoneau
authors.forename: Heidi
authors.initials: H
authors.lastname: Di Castillo
authors.forename: Virginie
authors.initials: V
authors.lastname: Siguret
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Bergmann
authors.forename: Eric
authors.initials: E
authors.lastname: Pautas
mesh_terms: D000208:Acute Disease; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000009:adverse effects*; D001835:Body Weight; D003404:Creatinine / Q000097:blood / Q000652:urine; D017984:Enoxaparin / Q000009:adverse effects*; D015951:Factor Xa / Q000378:metabolism; D065427:Factor Xa Inhibitors; D005260:Female; D006801:Humans; D007677:Kidney Function Tests; D008297:Male; D051437:Renal Insufficiency / Q000503:physiopathology*; D013923:Thromboembolism / Q000517:prevention & control
chemical_list: D000925:Anticoagulants; D017984:Enoxaparin; D065427:Factor Xa Inhibitors; D003404:Creatinine; D015951:Factor Xa