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Warfarin-fluoxetine and diazepam-fluoxetine interaction
1Talbert Medical Group, Salt Lake City, UT 84115, USA.
Pharmacotherapy
|January 1, 1997
Summary
Fluoxetine can dangerously interact with warfarin and diazepam, especially in elderly patients. This drug interaction led to a fatal cerebral hemorrhage and drug-induced delirium in one case.
Area of Science:
- Pharmacology
- Clinical Toxicology
- Geriatric Medicine
Background:
- Fluoxetine and its metabolite norfluoxetine are metabolized via the CYP450 system.
- Fluoxetine can inhibit the metabolism of other drugs.
- Potential drug interactions between fluoxetine, warfarin, and diazepam are not well-documented.
Observation:
- An elderly male patient was prescribed fluoxetine, warfarin, and diazepam concurrently.
- The patient experienced an elevated international normalized ratio (INR), indicative of a warfarin interaction.
- The patient developed drug delirium, suggesting inhibited diazepam metabolism.
Findings:
- The concurrent use of fluoxetine, warfarin, and diazepam led to a significant drug interaction.
- Inhibited diazepam metabolism by fluoxetine caused drug-induced delirium.
- Elevated INR due to fluoxetine-warfarin interaction resulted in a fatal cerebral hemorrhage.
Implications:
- Elderly patients on fluoxetine should avoid diazepam; lorazepam or oxazepam are safer alternatives due to hepatic conjugation.
- Close monitoring of INR is crucial for patients on warfarin when initiating or discontinuing fluoxetine.
- This case highlights the critical need for careful medication management and interaction monitoring in elderly patients.