PB0018 - Direct oral anticoagulant plasma levels in patients with low body weight: a retrospective study

Sunday, June 25, 2023

18:30 – 19:30 ET

Room: Exhibition

Presenting Author(s)

Anne-Laure Sennesael, MPharm MSc PhD

MPharm, MSc, PhD
Université catholique de Louvain, CHU UCL Namur, Namur Thrombosis and Hemostasis Center, NARILIS, Department of Pharmacy, Namur, Belgium
Namur, Namur, Belgium

Co-Author(s)

AL

Anne-Sophie Larock

MPharm, MSc
Université catholique de Louvain, CHU UCL Namur, NTHC, NARILIS, Department of Pharmacy, Namur, Belgium
Namur, Namur, Belgium
MH

Michael Hardy

MD
Université catholique de Louvain, CHU UCL Namur, NTHC, NARILIS, Anesthesiology Department, Namur, Belgium
Namur, Namur, Belgium
SL

Sarah Lessire

MD, PhD
Université catholique de Louvain, CHU UCL Namur, NTHC, NARILIS, Anesthesiology Department, Namur, Belgium
Namur, Namur, Belgium
AS

Anne Spinewine

MPharm, MSc, PhD
Université catholique de Louvain, CHU UCL Namur, NTHC, NARILIS, Department of Pharmacy, Namur, Belgium
Namur, Namur, Belgium
FM

François Mullier

MPharm, MSc, PhD
Université catholique de Louvain, CHU UCL Namur, NTHC, NARILIS, Hematology Laboratory, Namur, Belgium
Namur, Namur, Belgium

Background: Direct oral anticoagulants (DOAC) are increasingly used at extremes of body weight. However, DOAC pharmacokinetics may be significantly affected in this understudied population. Data are currently limited to support clinicians in decision making.

Aims: To describe DOAC plasma concentrations in patients with extremely low body weight.

Methods: We retrospectively analyzed DOAC measurements performed in clinical practice at the CHU UCL Namur between 2018 and 2022. Patients with a body weight ≤ 50 kg were included. We assessed the appropriateness of DOAC prescription based on drug labeling. DOAC peak and/or trough levels were estimated at steady-state using specific chromogenic assays. They were compared to on-therapy ranges observed in pivotal trials. Expected ranges were divided into quartiles, from Q1 (lower) to Q4 (upper). For each patient, risk factors for increased and decreased DOAC exposure were described (e.g. renal failure, drug-drug interactions).

Results: We included 22 patients (median weight 46 kg), who underwent 27 DOAC measurements. Apixaban was the most prescribed DOAC (n=19). Six patients received an inappropriate reduced dose (Table 1). DOAC peak or trough measurement was above the expected range for 8 patients (36%), including 2 patients with an inappropriate dose (full (n=1) and reduced (n=1)). Among the remaining 14 patients, 5 had at least one measurement in the upper quartile of the range (Q4). Lower-than-expected levels were not observed. Individual risk factors for increased and decreased DOAC levels are presented in Figure 1. The median number was 2 and 0 respectively, and did not differ between patients with measurement(s) above the range or within the range.

Conclusion(s): We observed higher-than-expected DOAC levels in a third of patients with low body weight. Off-label underdosing was common, but did not result in levels below the expected range. In clinical practice, DOAC measurement could help promote a safe use of DOAC in this population.