In 1951, Siede and Strohm 1 suggested a liver-function test with a sulfonamide preparation, the red dye azosulfamide (Prontosil Soluble, Bayer, or Neoprontosil, Winthrop). Azosulfamide is a sodium salt of an azo compound between sulfanilamide and a hydroxynaphthaline sulfonic acid with the formula shown in Figure 1.
About one-half of the administered dose is taken up by the liver cells. Part of this is then excreted unchanged in the bile,2 whereas the rest is broken down, probably by reductive enzymes.3 One of the metabolites seems to be sulfanilamide.4
The remainder of the azosulfamide, i. e., the part not removed by the liver, is excreted unchanged in the urine. The elimination occurs chiefly during the first 5 to 6 hours after the injection and is completed within 24 hours. The total amount of azosulfamide eliminated in the urine gives an indirect measure of the liver function with regard