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Malabsorption-associated warfarin resistance.
Brian J Sabol1, Ramon R Basa, Charles E Wilkins
1Department of Clinical Pharmacy, St. Elizabeth Health Center, Youngstown, OH 44501, USA. brian_sabol@hmis.org
This case study highlights warfarin resistance in a patient with recurrent thromboembolisms, likely due to malabsorption. Standard oral warfarin doses were ineffective, suggesting a gastrointestinal absorption defect.
Area of Science:
- Pharmacology
- Gastroenterology
- Hematology
Background:
- A 42-year-old male with a history of deep venous thrombosis (DVT), pulmonary embolism (PE), and myocardial infarctions presented with chest pain.
- The patient had multiple risk factors for thromboembolism and was on anticoagulation therapy.
Observation:
- The patient exhibited resistance to oral warfarin therapy, requiring significantly higher doses to achieve a therapeutic International Normalized Ratio (INR).
- Investigations ruled out common causes of drug interaction or malabsorption.
- Intravenous (IV) warfarin achieved therapeutic INR at a lower dose compared to oral administration, strongly suggesting malabsorption.
Findings:
- A diagnosis of warfarin malabsorption was made based on the differential response to oral versus IV administration.
- This condition contributed to the patient's recurrent thromboembolic events despite anticoagulation.
Implications:
- Warfarin malabsorption can lead to therapeutic failure and increased risk of thromboembolism.
- This case underscores the importance of considering malabsorption in patients with unexplained warfarin resistance.
- Alternative anticoagulation strategies or formulations may be necessary for patients with confirmed warfarin malabsorption.
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