The ASTHMA Pilot Study is a randomized, controlled, parallel group clinical trial of 6 weekly doses of azithromycin (cumulative dose 4800 mg) or placebo as adjunctive treatment in addition to usual care for adults with stable persistent asthma, with final follow up at 3 months after completion of study medication.

The hypothesis to be tested is that antibiotic treatment will improve asthma at followup, and that this improvement will be limited to patients with evidence of C. pneumoniae infection.

The secondary hypothesis is that randomized, controlled treatment trials can be carried out successfully in a geographically dispersed practice-based research network.

Asthma is a chronic inflammatory bronchial condition of unknown etiology. Decades ago many clinicians believed that infection played a major role in asthma etiology, but current expert opinion favors the view that asthma is a noninfectious condition whose root cause is inflammation. Therefore chronic antiinflammatory therapy, mainly inhaled corticosteroids, is currently advocated as primary anti-asthma treatment. It is important to recognize, however, that antiinflammatory therapy is palliative, not curative.

A growing body of evidence implicates chronic bronchial infection with Chlamydia pneumoniae in the pathogenesis of asthma in both adults and children. Organism identification studies (culture and PCR) suggest that up to one-half of children with asthma may be chronically infected by C. pneumoniae, and seroepidemiologic studies in adults are consistent with chronic C. pneumoniae infection in the majority of adult-onset asthmatics. Furthermore, case reports and uncontrolled trials have provided provocative but inconclusive evidence that treatment of C. pneumoniae infection in both children and adults with asthma can favorably affect the natural history of this disorder.

We propose a randomized, placebo-controlled, triple-blinded study of antichlamydial antimicrobial therapy in adult-onset asthma. Results will help to determine whether antimicrobial therapy is effective in treating some adult asthma syndromes. Positive results would have significant public health implications. Methodologies developed for use in this trial may expedite future studies in practice-based research networks.

Inclusion Criteria:

• adults with stable persistent asthma and evidence for reversible airway obstruction

Exclusion Criteria:

• macrolide allergy, pregnancy or lactation, specified comorbidities or medications