A short (3-day) course of azithromycin tablets versus a 10-day course of amoxycillin-clavulanic acid (co-amoxiclav) in the treatment of adults with lower respiratory tract infections and effects on long-term outcome.

The efficacy and safety of a 3-day regimen of azithromycin prescribed in the new tablet form and of a 10-day regimen of amoxycillin clavulanic acid (co-amoxiclav, Augmentin) were compared in patients with acute lower respiratory tract infections. Of the 144 enrolled patients, 123 had a Type 1 acute exacerbation of chronic bronchitis (AECB), three patients had pneumonia, and 18 had purulent bronchitis. Treatment was successful, defined as cure or major improvement on day 14, in 59/62 (95%) patients in the azithromycin treatment group compared with 54/61 (90%) patients in the co-amoxiclav. At 30 days, the incidence of success was 77% (48/62) in the azithromycin treated group, compared with 66% (40/61) of co-amoxiclav-treated patients. At 60 days, incidences were 66% (41/62) and 59% (36/61), respectively. Several pathogens were isolated: Haemophilus influenzae in 21 patients (minimum inhibitory concentration (MIC) range for azithromycin 0.12-4 mg/l; co-amoxiclav 0.25-4 mg/l); Streptococcus pneumoniae in nine (MIC azithromycin < or = 0.06 > or = 256 mg/l; co-amoxiclav < or = 0.06-1 mg/l); and Moraxella catarrhalis in 11 (MIC azithromycin < or =0.06-2 mg/l; co-amoxiclav < or = 0.06-0.5 mg/l). Microbiological response rates were comparable. A significant correlation between clinical and microbiological cure was found (p = 0.02, power 0.6). In 15 (10%) patients, positive serology for viruses or atypical pathogens was found. In the co-amoxiclav-treatment group, 24 patients had mild adverse events (12 diarrhoea), compared with 27 treated with azithromycin (p = 0.47). It is concluded that a 3-day regimen of azithromycin prescribed as tablets is as clinically and microbiologically effective as a 10-day regimen of co-amoxiclav in the treatment of acute lower respiratory tract infections. Moreover, since the percentage of viral infections was low and a significant correlation between microbiological and clinical cure was found, this study shows that clinical symptoms can be used to establish which patients with AECB (Type 1) should be treated with antimicrobial agents.