Background Exposure to enoxaparin is significantly increased in patients with severe renal impairment (creatinine clearance ClCr <30 mL/min). Thus, a dose adjustment is recommended for both the therapeutic and prophylactic dose ranges.

Purpose To evaluate the predictive ability of different formulas to estimate renal function, based on ClCr or the estimated glomerular filtration rate (eGFR), in a series of patients receiving treatment doses of enoxaparin.

Materials and methods Observational, retrospective, cross-sectional study, in patients treated with subcutaneous enoxaparin twice daily and with available records of peak anti-factor Xa activity (anti-Xa) levels (4 h after administration), over five months (Jan–May 2013) in a third-level hospital. Demographic and analytical data were recorded; and also dose/body-weight and peak anti-Xa level. Renal function was estimated according to the following formulas: Cockcroft-Gault (CG), MDRD6, MDRD4-IDMS and CKD-EPI. The predictive ability, calculated by using the determination coefficient (% of variability explained) of the different formulas for the estimation of renal function was evaluated by using a univariate linear regression model.

Results Data from 83 patients were included in the analysis. Demographic data were mean age (SD) 66 years (17), 65% female and 99% Caucasian. Of them, 37.7% of patients had prostheses, 28.6% had atrial fibrillation and 25.5% had suffered a thromboembolic event. The mean values for dose/body-weight, anti-Xa at peak and serum creatinine were 0.72 mg/kg (0.25), 0.66 IU/mL (0.30) and 1.28 mg/dL (0.93) respectively. The estimates of renal function by the different formulas were: 77.4 ml/min (58.8) –CG, 62.6 ml/min/1.73m2 (38.5) –MDRD6, 94.9 ml/min/1.73m2 (73.9) –MDRD4-IDMS, and 67.3 ml/min (38.2) –CKD-EPI.

Only CKD-EPI showed significant association with the effective dose of enoxaparin (P = 0.026), although a trend toward the association was observed with the other formulas (P = 0.073 for MDRD6 and P = 0.11 for CG); MDRD4-IDMS showed no association (P = 0.267).

The coefficient of determination varied between the different formulas: 17.1% for CG; 15.7% for MDRD4–IDMS; 19.5% for CKD-EPI; 19.6% for MDRD6. The estimated equation for anti-Xa based on dose/kg and eGFR (using CKD-EPI) is: aXa = 0.3 + 0.722dose/kg – 0.02CKD-EPI.

Conclusions Exposure to enoxaparin is significantly increased in patients with severe renal impairment. However, the predictive capacity of the different eGFR formulas varied from 15.7 to 19.6%, and only CKD-EPI showed a significant association.

No conflict of interest.