Absorption of Antibiotics from the Rat Lung 1

Abstract

Summary

Five antibiotics were administered intratracheally as solutions to anesthetized rats. The times necessary for 50% absorption ranged from 1.9 to 33 min. Chloramphenicol was absorbed most rapidly followed by doxycycline, erythromycin, and tetracycline, with benzylpenicillin showing the slowest rate. A comparison of pulmonary absorption rate, molecular weight, and lipoid (chloroform)/water partition coefficient of the drugs indicated that lipoid solubility is more important than molecular size in determining the relative absorption rates. The absorption process for benzylpenicillin, doxycycline, and erythromycin did not become saturated when drug concentrations were raised 10-5000-fold, suggesting that these antibiotics are absorbed mainly by a process of simple diffusion.

The authors are indebted to Mrs. Jean C. Henderson for her excellent technical assistance.