Does Azithromycin and Cetirizine Combination Given for Upper Respiratory Tract Infections has any Significant Effect on QTc?

Introduction: Azithromycin usage in patients with baseline cardiovascular risk is associated with increased risk of cardiovascular mortality, following which Food and Drug Administration (FDA) issued a black box warning regarding safety of azithromycin in patients with cardiovascular morbidity particularly with prolonged QTc. Cetirizine is a second generation anti histaminic and is found to be commonly used for Upper Respiratory Tract Infections (URIs) along with azithromycin on outpatient basis. Whether, usage of these two drugs in combination confers a similar risk, is unknown.

Aim: To assess the effect on QTc among patients treated with azithromycin and cetirizine combination for upper respiratory tract infection.

Materials And Methods: We conducted a prospective longitudinal study from August 2014 to July 2016. The study was done on 45 patients above 18 years of age without any cardiovascular morbidity in whom azithromycin and cetirizine were prescribed for upper respiratory tract infections. We compared the QTc on day 1 and day 4. Data was analysed using Student's paired t-test.

Results: During three days of azithromycin and cetirizine for upper respiratory tract infections, we observed that on day 4 there was significant increase in QTc in 43 patients (95.6%) as compared with the QTc on day 1. We also observed that in 8 (17.8%) out of 45 patients, QTc on day 4 crossed the upper limit of normal {430 milliseconds (ms)}, but this was not statistically significant. However, analysing these eight patients, we obtained the baseline QTc of 377.50 ms above which if prescribed, this combination of drugs have a chance of prolonging the QTc above 430 ms with a sensitivity of 87.5% and specificity of 40.5%.

Conclusion: During three days treatment with azithromycin and cetirizine, there was significant change in QTc between day 1 and day 4. Patients with baseline QTc greater than 377.5 ms were at risk of QTc prolongation above 430 ms on day 4.