Impact of ileostomy creation on apixaban plasma concentrations: a retrospective case-series

BACKGROUND:
Apixaban is a direct-acting oral anticoagulant indicated for stroke and systemic embolism prevention in atrial fibrillation (AF) and for the treatment of venous thromboembolism (VTE). It is absorbed throughout the small intestine, with possible contribution from the distal ileum and ascending colon. The effect of ileostomy creation, which excludes the colon from the gastrointestinal tract, on apixaban plasma concentrations remains unclear.


OBJECTIVES:
To evaluate the impact of ileostomy creation on apixaban plasma concentrations.


DESIGN:
Retrospective case series


SETTING:
A single tertiary care center in Saudi Arabia


PATIENTS AND METHODS:
Patients receiving apixaban who had peak apixaban plasma concentrations measured following ileostomy creation between January 2021 and June 2025 were included. Patients were followed for at least three months and up to 12 months, or until ileostomy closure, discontinuation of apixaban, or death, whichever occurred first.


MAIN OUTCOME MEASURES:
Peak apixaban plasma concentrations, proportion of patients within the expected 5th-95th percentile range reported in Phase II and Phase III trials, the distribution of apixaban plasma concentrations below or above the median of the expected range, and clinical bleeding or thrombotic events.


SAMPLE SIZE:
Ten patients


RESULTS:
Apixaban was prescribed for VTE in six patients and AF in four. Eight patients (80%) had peak apixaban concentrations within the expected 5th-95th percentile range of apixaban concentrations; one patient was below the 5th percentile, and one was above the 95th percentile. Six patients had apixaban plasma peak concentrations below the median of the expected 5th-95th percentile range. Two patients experienced rectal bleeding, and no thrombotic events were observed.


CONCLUSIONS:
In patients with an ileostomy, apixaban peak concentrations generally fall within the expected 5th-95th percentile range, though frequently below the median. Ileostomy may slightly affect apixaban absorption, but does not appear to result in underexposure. Standard apixaban dosing seems appropriate.


LIMITATIONS:
Small sample size, lack of control, and retrospective design.