Intermittent azithromycin treatment for respiratory symptoms in patients with chronic Chlamydia pneumoniae infection.

Chlamydia pneumoniae (Cpn) is a common respiratory pathogen with a biphasic replicative cycle and has a tendency to cause chronic infections. Azithromycin is commonly used for the treatment of Cpn infections, but little is known about the optimal dose and duration of therapy. In this prospective double-blind, randomized study the effects of azithromycin and placebo were compared regarding longstanding airway and/or pharyngeal symptoms in patients with chronic Cpn infection. Further, effects on antibody titres and lung function were assessed. 103 patients were treated with either azithromycin 500 mg daily for 5 d, repeated 3 times with a 23-d interval, or placebo. Patients were examined 4 months and 1 y after completed treatment. Evaluation of symptoms showed general improvement and less hawking in patients treated with azithromycin compared to placebo after 4 months, but there was no sustained difference 1 y after completed treatment. The antibody titres remained stable, and there was no influence on lung function. Adverse events, primarily gastrointestinal, were more frequently reported with azithromycin than placebo. In conclusion, azithromycin was effective for reduction of respiratory symptoms in patients with chronic Cpn infection, but prolonged intermittent treatment with high doses did not eradicate the chronic infection.