DALTEPARIN THROMBOPROPHYLAXIS IN CRITICALLY ILL PATIENTS WITH SEVERE RENAL INSUFFICIENCY: THE DIRECT STUDY

Differences among Various Low-Molecular-Weight Heparins in Patients with Severe Renal Insufficiency: An Analysis of Recent Clinical Trials

Background: Primarily eliminated by the kidneys, low-molecular-weight heparins (LMWHs) need to be monitored carefully when used in patients with severe renal insufficiency, because of the concern about bioaccumulation, which can increase the risk of bleeding. Individual LMWHs have not been compared with each other in large clinical trials, and currently there is no standard of practice for the use of LMWH in this patient population.

Methods: Computerized queries of PubMed, MEDLINE, and the American Society of Hematology abstract database were performed to identify clinical trials assessing the safety of LMWHs in patients with severe renal failure (creatinine clearance [CrCl] <30 mL/min).

Results: A meta-analysis of 15 studies of enoxaparin and 2 studies of tinzaparin (N = 5201) showed that when compared with patients with a CrCl >30 mL/min, those with a CrCl ≤30 mL/min had more than double the risk of major bleeding and higher peak anti-Xa levels (Lim et al, 2006). Much of this effect was confined to patients who received standard therapeutic doses of enoxaparin (Mahe et al, 2007). A study of medical patients with a reduced CrCl treated with tinzaparin or enoxaparin showed significantly increased mean anti-Xa activity in the enoxaparin group but not in the tinzaparin group, indicating a significant accumulation of enoxaparin but not of tinzaparin (Mahe et al, 2007). Recent data suggest that dalteparin, when used at prophylactic doses, does not bioaccumulate and can be used safely in patients with severe renal impairment (Tincani et al, 2006; Douketis et al, 2007).

Conclusions: Whereas studies suggest that enoxaparin bioaccumulates in patients with severe renal insufficiency (Mahe et al, 2007), dalteparin and tinzaparin do not appear to bioaccumulate to the same degree (Tincani et al, 2006; Mahe et al, 2007; Douketis et al, 2007). These differences may be explained by the fact that smaller LMWH chains (enoxaparin) are cleared primarily by the kidneys, whereas larger chains (dalteparin, tinzaparin) have greater clearance by nonrenal mechanisms. Thus, dalteparin and tinzaparin may be preferred in patients with renal impairment.

Table. Summary of recent trials evaluating dalteparin and tinzaparin in patients with renal impairment

Trial Study Design/Regimen Results CrCl = creatinine clearance; DIRECT = Dalteparin’s Influence on Renally Compromised: Anti-Ten-A Study; DVT = deep vein thrombosis; SC = subcutaneous. Tincani et al, 2006 N = 115 Patients with acute medical illness and elevated serum CrCl
 Dalteparin 2500 IU (low-risk patients) or 5000 IU (high-risk patients) SC once daily for ≥6 days No evidence of dalteparin bioaccumulation (increased anti-Xa levels) on Day 6, irrespective of renal function
 No correlation between degree of renal impairment and peak anti-Xa level on Day 6 No major bleeding or DVT events DIRECT (Douketis et al, 2007) N = 138 Critically ill patients with CrCl <30 mL/min
 Dalteparin, 5000 IU SC once daily for ≤30 days No evidence of dalteparin bioaccumulation Median trough anti-Xa level <0.1 IU/mL
 Major bleeds occurred in 10 patients (7.2%), all with trough anti-Xa <0.12 IU/mL DVT occurred in 7 patients (5.1%) Mahe et al, 2007 N = 55 Elderly medical patients with a baseline CrCl between 20 and 50 mL/min
 Enoxaparin 4000 IU SC or tinzaparin 4500 IU SC once daily for 8 days The accumulation factor was not significant for tinzaparin (1.05, P= 0.29), whereas it was significant for enoxaparin (1.22, P<0.0001) by Day 8
 No patient in the study had a thromboembolic event 4 patients given enoxaparin had bleeding events (1 major) vs 5 in the tinzaparin group (2 major)