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QT prolongation associated with azithromycin/amiodarone combination
P Samarendra1, S Kumari, S J Evans
1Department of Cardiology, Long Island College Hospital, Brooklyn, New York, USA. Padmaraj@aol.com
Abstract:
Administration of oral azithromycin, in addition to previously well-tolerated long-term amiodarone therapy, was associated with a marked prolongation of QT interval and increased QT dispersion, both substrates for life-threatening ventricular tachyarrhythmia and torsades de pointes. This is a report of QT prolongation and increased QT dispersion associated with the use of azithromycin. The report assumes an added significance, in view of widespread empirical use of this antibiotic for the treatment of lower respiratory infections and belief of its safety in patients with cardiac diseases. Based on the authors' experience, they would like to emphasize that the combination of azithromycin with other drugs known to prolong QT or causing torsades de pointes be used with caution until the question of the proarrhythmic effect of azithromycin is resolved by further studies.
Insights
Azithromycin combined with amiodarone may prolong the QT interval, increasing the risk of dangerous heart rhythms like torsades de pointes. Caution is advised when using azithromycin with other QT-prolonging drugs.
Area of Science:
- Cardiology
- Pharmacology
- Clinical Medicine
Background:
- Long-term amiodarone therapy is generally well-tolerated.
- Azithromycin is widely used for respiratory infections, often presumed safe in cardiac patients.
Observation:
- A case of QT prolongation and increased QT dispersion was observed.
- This occurred during concurrent administration of oral azithromycin and amiodarone.
Findings:
- The combination of azithromycin and amiodarone led to significant QT interval prolongation.
- Increased QT dispersion was also noted, a risk factor for ventricular arrhythmias.
Implications:
- This highlights a potential proarrhythmic effect of azithromycin, particularly in combination therapy.
- Caution is recommended when prescribing azithromycin with other QT-prolonging medications pending further research.