Pharmacokinetics of azithromycin and erythromycin in human endometrial epithelial cells and in cells infected with Chlamydia trachomatis.

The pharmacokinetics of azithromycin and erythromycin were examined in uninfected and Chlamydia trachomatis infected human endometrial epithelial cells in vitro. Cells which were grown in a polarized orientation showed a three-fold higher quantity of azithromycin uptake than did non-polarized cells. Cellular penetration profiles of azithromycin exceeded erythromycin by as much as eight-fold. In addition, approximately 20% of azithromycin remained cell-associated after 24 h in drug-free medium whereas erythromycin was not retained beyond 3 h. Hormone-responsive primary human endometrial gland epithelial cells, cultured directly after hysterectomy, showed enhanced uptake of both antimicrobials compared with laboratory adapted epithelial cell lines. Cells infected with a genital serovariant of C. trachomatis showed no significant difference in antibiotic uptake during the early stages of the chlamydial developmental cycle, and only a slight decrease in azithromycin uptake in the late stage of infection compared with non-infected cells. Morphological evidence of the bactericidal activity of azithromycin was evident in infected cells at most stages of the chlamydial developmental cycle, whereas the same concentration of erythromycin produced less evidence of marked bactericidal activity as observed by transmission electron microscopy.