Anti-Xa Levels and Renal Function: Analysis of the First 32 Patients in the Tinzaparin in Renal Insufficiency for Venous Thromboembolism Study.

Abstract Background: Low-molecular-weight heparin (LMWH) is renally eliminated; its use in patients with renal insufficiency may be associated with accumulation and an increased bleeding risk. Due to its higher molecular weight and greater negative charge, tinzaparin may be less dependent on renal elimination compared to other LMWHs. As a result, tinzaparin may be less prone to accumulate in patients with renal insufficiency. Purpose: To measure the anticoagulant effect of a 5-day course of therapeutic-dose tinzaparin used for the initial treatment of venous thromboembolism (VTE) in patients with varying degrees of renal insufficiency. We present the anti-Xa results of the first 32 patients enrolled in the study, correlated with renal function. Design: Prospective cohort study. Methods: In- and out-patients requiring therapeutic dose anticoagulation were enrolled and stratified into 4 groups based on creatinine clearance (CrCl): > 60 ml/min, 30–60 ml/min, ≤ 30 ml/min and hemodialysis-dependent. Tinzaparin 175 IU/kg was administered once daily for 5 days or until the INR was ≥ 2.0 with warfarin therapy. Trough anti-Xa levels were measured prior to the 3rd (day 3) and 5th (day 5) tinzaparin doses. Patients with an anti-Xa level > 0.5 IU/mL received tinzaparin dose adjustment using a standardized nomogram. Results: The relationship between anti-Xa levels and CrCl is shown in figure 1. One patient with a CrCl of 47 ml/min had a day 3 anti-Xa level of 0.62 IU/ml and required dose adjustment, resulting in a day 5 anti-Xa of 0.22 IU/ml. There has been one minor bleeding event (hematoma) following a traumatic intravenous catheter insertion. No major bleeding or recurrent VTE events have occurred. Conclusions: In a cohort of 32 patients with differing degrees of renal function including patients requiring hemodialysis, use of therapeutic-dose tinzaparin for 5 days does not appear to result in accumulation of the anticoagulant effects. There is no apparent correlation between anti-Xa level and renal function. Our results support ongoing evaluation of tinzaparin in patients with severe renal insufficiency. Figure 1. Anti-Xa levels an renal function Figure 1. Anti-Xa levels an renal function