Use of 4-Aminoantipyrine for Determining Volume of Body Water Available for Solute Dilution

Because of the difficulty and inaccuracy of antipyrine determinations, 4AA (4-aminoantipyrine, 1-phenyl-2,3-dimethyl-4-amino-pyrazolone-5) was investigated as a means of measuring tissue water contents. Rapid, simple and accurate analysis by diazotization and acid coupling with N-1-naphthyl ethylene diamine was employed. Uniform distribution of 4AA between erythrocyte and plasma water, and between the water contents of various organs of dogs, goats and men was found. It was freely diffusible from plasma and cells but totally excluded from fat in vivo. The volume of distribution in men was equal to, or slightly less than, that of simultaneously injected antipyrine and it was metabolized by the body at a very slow exponential rate without any recognizable pharmacologic action.