Levels of azithromycin and alpha-1 acid glycoprotein in serum in patients with community-acquired pneumonia.

After an oral dose of 500 mg of azithromycin in patients with community-acquired pneumonia, their serum concentrations ranged between 0.06 and 0.25 mg/liter during the first 12 hours; the calculated percentages of unbound drug varied between 45 and 86%. This study shows that in these patients, the total levels of azithromycin in serum are lower than those expected and that the percentage of bound drug is clinically irrelevant.