A nurse is caring for a client who is prescribed with azithromycin for pertussis. Which of the following is a complication of this medication that can cause cardiac dysrhythmias?

A. Incorrect: Tooth discoloration is not a known complication of azithromycin. B. Incorrect: Photosensitivity is more common with tetracyclines, not azithromycin. C. Correct: Azithromycin can prolong the QT interval, increasing the risk of life-threatening arrhythmias such as torsades de pointes. D. Incorrect: Azithromycin does not shorten the QT interval.