Low molecular weight heparins in patients with renal insufficiency.

Low molecular weight heparins (LMWHs) have been evaluated in a large number of randomized clinical trials and have been shown to be safe and effective for the prophylaxis and treatment of thromboembolic disorders, myocardial infarction and unstable angina in patients with normal renal function. Unfortunately moststudies evaluating LMWH have excluded patients with renal insuffciency, -or those that included these patients were exceedingly small. There are limited clinical data to make assumptions about how to offer the same benefits of LMWH in patients with renal insufficiency. Several small pharmacokinetic studies of the LMWH enoxaparin have demonstrated that there is a delay in elimination in patients with renal insufficiency. There are limited data to make the same assumption concerning other LMWH. This accumulation effect could place these patients at an increased risk of bleeding. Monitoring of LMWH by measuring antifactor Xa levels may be an option. However, the ideal therapeutic range for LMWH for which there is proven efficacy and low risk of bleeding has not been clearly defined Empirically adjusted doses or lower doses intended for prophylaxis or for hemodialysis extra-corporeal anticoagulation may not demonstrate the same level of accumulation, however, studies are limited and ofshort duration. The use of measuring antifactor Xa levels remains warranted in patients with CrCl < 30 mL/min treated with empirically adjusted doses and prophylactic doses used for duration of> 4 days. Until there are better data to suggest otherwise, adjusted doses of enoxaparin are not first choice in patients with renal insufficiency when other options exist. Heparin remains the gold standard of treatment in patients with renal insufficiency.