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Concomitant digoxin toxicity and warfarin interaction in a patient receiving clarithromycin
M J Gooderham1, P Bolli, P G Fernandez
1University of Western Ontario, London, Canada.
Clarithromycin can interact with warfarin and digoxin, increasing toxicity risks. Healthcare providers should monitor patients for potential adverse drug events when these medications are co-prescribed.
Area of Science:
- Pharmacology
- Clinical Medicine
- Drug Interactions
Background:
- Warfarin and digoxin are commonly prescribed for atrial fibrillation.
- Clarithromycin is a macrolide antibiotic used for bacterial infections.
- Drug interactions pose significant risks in polypharmacy.
Observation:
- A 72-year-old woman on digoxin and warfarin developed toxicity after starting clarithromycin.
- The patient presented with gastrointestinal symptoms, weakness, dizziness, and visual changes.
- Lab results showed elevated digoxin levels and a high international normalized ratio.
Findings:
- Clarithromycin inhibited warfarin metabolism via cytochrome P450, increasing INR.
- Clarithromycin altered gut flora, increasing digoxin absorption and toxicity.
- Discontinuation and dose adjustment of medications resolved the adverse events.
Implications:
- Clarithromycin poses a risk of significant drug interactions with both warfarin and digoxin.
- Clinicians must be vigilant for drug interactions, especially with macrolide antibiotics.
- Monitoring patients for symptoms and laboratory changes is crucial to prevent severe complications.
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