Pharmacokinetics of azithromycin after single oral dosing of experimental animals.

Azithromycin, a macrolide antibiotic with an enhanced antimicrobial spectrum, was found to have a longer half-life than erythromycin, with marked tissue penetration. The pharmacokinetics of azithromycin after oral administration were compared with those of erythromycin in rats (200 mg kg-1) and rabbits (80 mg kg-1). Concentrations of azithromycin in liver, lung, kidney, ileum, and brain were higher than serum concentrations. The slow decline in tissue concentrations was evident from the biphasic elimination profile. Thus, advantageous pharmacokinetic properties and the broader antimicrobial spectrum of azithromycin relative to erythromycin appear to further support its therapeutic potential.