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Is azithromycin treatment associated with prolongation of the Q-Tc interval?
1Department of Infectious Diseases, University Medical Centre Ljubljana, Slovenia. franc.strle@mf.uni-lj.si
Objectives:
Prolongation of the corrected Q-T (Q-Tc) interval is associated with a risk of severe and even life-threatening arrythmias. It may occur as an adverse effect of various pharmacological agents including macrolides. We opted to study the influence of the azalide antibiotic azithromycin on the duration of Q-Tc interval as data on this subject are limited.
Methods:
A prospective study was performed on 47 patients, 31 females and 16 males, aged 19-77 (median 52) years, treated with azithromycin (total dosage 3 g, divided over 5 days) for typical solitary erythema migrans. The patients were previously healthy and were not receiving any other medication. In all of them ECGs were performed before as well as 7 and 14 days after initiation of the azithromycin therapy. Thus, a total of 141 ECG tracings were analyzed. Q-T intervals were measured manually in a blinded manner and corrected for heart rate according to Bazzet's formula: Q-Tc = measured Q-T (ms)/square root of R-R (s).
Results:
Comparison of the Q-Tc intervals before, 7 days, and 14 days after the initiation of azithromycin treatment revealed a mild, but not significant prolongation (median values 406, 412.5 and 419 ms with ranges of 339-488, 352-510, and 346-505 ms, respectively). Q-Tc intervals exceeding the upper normal value of 440 ms were found in the same proportion of patients prior to as after institution of treatment. None of the ECG tracings showed significant arrhythmias.
Conclusion:
In previously healthy persons, a modest statistically insignificant prolongation of the Q-Tc interval without clinical consequences was observed after completion of a course of 3 g of azithromycin administered over a period of 5 days for solitary erythema migrans.
Insights
Azithromycin, an antibiotic, showed a mild, insignificant prolongation of the corrected Q-T (Q-Tc) interval in patients treated for Lyme disease. This effect did not lead to significant arrhythmias or clinical consequences in healthy individuals.
Area of Science:
- Pharmacology
- Cardiology
- Infectious Diseases
Background:
- Prolongation of the corrected Q-T (Q-Tc) interval is a known risk factor for serious cardiac arrhythmias.
- Macrolide antibiotics, including azithromycin, have been implicated in Q-Tc interval prolongation.
- Limited data exist on the specific effects of azithromycin on Q-Tc duration.
Purpose of the Study:
- To investigate the influence of the azalide antibiotic azithromycin on Q-Tc interval duration.
- To assess potential cardiac risks associated with azithromycin treatment in patients with erythema migrans.
Main Methods:
- Prospective study of 47 previously healthy patients treated with azithromycin (3g over 5 days) for erythema migrans.
- Electrocardiograms (ECGs) were performed before, and 7 and 14 days after azithromycin initiation.
- Q-Tc intervals were manually measured and corrected for heart rate using Bazett's formula.
Main Results:
- A mild, statistically insignificant prolongation of the Q-Tc interval was observed.
- Median Q-Tc values showed a slight increase from baseline but remained within normal limits for most patients.
- No significant arrhythmias were detected, and the proportion of patients with Q-Tc intervals exceeding 440 ms did not change.
Conclusions:
- A 5-day course of azithromycin (3g) for erythema migrans resulted in a modest, statistically insignificant Q-Tc interval prolongation in healthy individuals.
- The observed Q-Tc prolongation did not lead to clinically significant consequences or arrhythmias.
- Azithromycin appears to have a limited impact on Q-Tc interval in this patient population.