Absorption of Heparin and Cyanocobalamin from the Rat Lung 1

Abstract

Summary

Solutions of heparin and cyanocobalamin were administered through a tight-fitting tracheal cannula into the lungs of anesthetized rats. The times necessary for 50% absorption from the lungs were 3 hr for cyanocobalamin and 9.2 hr for heparin. The absorption process did not become saturated when drug concentrations were raised 100 to 1000-fold, suggesting that both compounds are absorbed mainly by a process of simple diffusion. A comparison of pulmonary absorption rates and diffusion coefficients of heparin and cyanocobalamin with corresponding values reported previously for other lipoid-insoluble compounds indicated that observed absorption rates were close to the rates predicted for the two drugs based on their calculated diffusion coefficients and the view that absorption occurs mainly through membrane pores.