A Clinical Practice-Based Comparison of Conventional and Individualized Dosing Strategies for Therapeutic Enoxaparin

To understand differences in anti-factor-Xa levels produced by two different dosing strategies (conventional and individualized) for therapeutic enoxaparin in a cohort of hospital inpatients. A multicenter, retrospective cohort study over a two- and a half-year period for inpatients with stable renal function and on therapeutic enoxaparin. Anti-factor-Xa levels were taken 3-5 h after enoxaparin administration and a minimum of 48 h of dosing. The final analysis included 278 patients from five hospitals: conventional dosing was used for 141, while 137 were given an unconventional dose, that is, individualized for their renal function and weight. Out-of-range levels were frequent (35% to 40% of all inpatients). After adjustment for age, renal function, and body mass index (BMI), the conventional group was more likely to experience above-range levels (> 1.0 IU/mL; OR 2.50 [95% CI 1.38-4.56], p < 0.003) than the individualized group. Individualized dosing was independently associated with higher odds of a below-range anti-Xa level (< 0.5 IU/mL) compared to conventional dosing (OR 2.27 [95% CI 1.07-4.76], p = 0.03). Within the conventional group, above-range levels were significantly and independently associated with decreasing renal function (OR 0.97, 95% CI 0.96-0.99, p = 0.004) and with increasing BMI (OR 1.06, 95% CI 1.01-1.10, p = 0.02). No such associations were seen with an individualized approach. Clinical event rates were low and not different between groups (p > 0.24). Conventional therapeutic dosing of enoxaparin exposed people with obesity or renal impairment to more frequent above-range anti-factor-Xa levels; individualizing the dose could improve this but might expose people to subtherapeutic levels. More research is needed.