Cephalexin concentrations in sputum during acute respiratory infections

In 20 patients with acute pulmonary infections, sputum purulence, sputum volume, and concentration and excretion of cephalexin in the sputum significantly decreased concurrently during therapy. The concentration of cephalexin in the serum remained unchanged. Significant correlations were observed between drug concentrations in sputum and serum and between drug excretion in sputum and concentration in serum. These observations may be explained by decreased integrity of the "blood-bronchus barrier" during inflammation, with diffusion of serum into bronchial mucus, without the necessity of postulating active transport.