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Rivaroxaban Plasma Concentrations Cannot be Predicted from Coagulation Assays: Real-Life Experience From a Tertiary
Yassar Alamri1,2, Milan Sundermann2, Adele O'Mahony1
1Department of Clinical Pharmacology, Christchurch Hospital, Christchurch, New Zealand.
Therapeutic Drug Monitoring
|July 16, 2025
Summary
Direct oral anticoagulants like rivaroxaban are preferred, but predicting concentrations is challenging. This study found no accurate mathematical model using routine tests to predict rivaroxaban levels.
Area of Science:
- Pharmacology
- Clinical Chemistry
- Internal Medicine
Background:
- Direct oral anticoagulants (DOACs) are increasingly preferred over vitamin K antagonists.
- Measuring plasma concentrations of DOACs like rivaroxaban may offer clinical benefits in specific scenarios.
- Understanding rivaroxaban levels is crucial for optimizing patient care.
Purpose of the Study:
- To describe clinical experiences with rivaroxaban in adult patients.
- To develop a mathematical model for predicting rivaroxaban concentrations using routine coagulation screening assays.
Main Methods:
- Prospective data collection over 4 years.
- Inclusion of patient characteristics, plasma rivaroxaban concentrations, and coagulation assays (PT, aPTT, TCT).
- Statistical analysis to establish relationships and model development using linear regression.
Main Results:
- 403 rivaroxaban concentrations were analyzed (median 66 mcg/L).
- Common indications for measurement included postinitiation monitoring, thromboembolic/bleeding events, and dose adjustments.
- Dose adjustments occurred in 21% of patients; significant relationships between PT/aPTT and rivaroxaban levels were observed, but a predictive model was unsuccessful.
Conclusions:
- Measured rivaroxaban concentrations showed wide variability, necessitating diverse clinical indications for measurement.
- A significant proportion of measurements led to dosing adjustments, highlighting the need for defined reference ranges.
- An accurate mathematical model to predict rivaroxaban concentrations from routine coagulation assays could not be developed.
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