Abstract
1. While the isotonic phosphate buffer (pH 6.0∼6.4) was recirculatingly perfused through the rat small intestine for 3 hours, volume of the solution was constant. 2. When the isotonic phosphate buffered solution (pH 6.0∼6.4) containing sulfonamide was recirculatingly perfused through the rat small intestine in vivo, the logarithm of residual ratio of the drug vs. time curve was a straight line. 3. From the slope of the straight line, apparent permeability coefficient, pa, was obtained. The constants were : Sulfaguanidine (0.0×10-3 cm./min.) ; Sulfathiazole (0.9×10-3) ; Sulfanilamide (1.0×10-3) ; Sulfamethoxypyridazine (1.7×10-3) ; Sulfisomezole 3.2×10-3). 4. It may be suggested that the permeability coefficient of sulfisomezole from intestinal lumen (isotonic phosphate buffered solution at pH 6.0∼6.4) into plasma is much larger than that from plasma into intestinal lumen. 5. The Pa-pH diagrams of four sulfonamides were obtained.
