Sputum antimicrobial levels and clinical outcome in bronchitis.

The role of antimicrobials in the treatment of bronchitis remains controversial. Antimicrobials are rarely indicated in acute bronchitis. Antimicrobials are indicated in a subset of patients with acute exacerbations of chronic bronchitis. The efficacy of an antimicrobial agent in bronchitis can be estimated by the ratio of the sputum concentration of the antimicrobial to its in vitro activity against common respiratory pathogens (S/M90). These S/M90 rates are presented in tabular form. However, given the lack of solid data to support antimicrobial treatment for most episodes of bronchitis, use of the S/M90 to select antimicrobial therapy remains theoretical rather than of proven clinical benefit.