Studies on Absorption and Excretion of Drugs. III. Kinetics of Penetration of Sulfonamides through the Intestinal Barrier in Vitro

Abstract

1. The penetration ofsulfonamides through the rat small intestine was investigated from the physicochemical standpoint in vitro.
2. Theoretical equations for the penetration mechanism of sulfathiazole were derived from the assumption that it penetrates through intestinal barrier in its three forms at the respective penetration rates.
3. From the data obtained, the respective permeability coefficients for the undissociated, alkaline and acid forms of sulfathiazole, P₁, P₂, and P₃ were statistically determined. The estimated values of P¹, P₂, and P₃ were 0.00064, 0.00979, 0.00132 (cc./cm./min.), respectively.
4. The experiment at the equilibrium state was attempted in order to examine the validity of the theoretical equation. Satisfactory results are obtained for P₁ and P₃, but not for P₂.
5. The penetration rates of fivesulfonamides were compared at the same pH value. The penetration rates were in the following order: sulfisomezole>sulfamethoxypyridazine<sulfanilamide<sulfathiazole<sulfaguanidine.