The Evaluation of Iodinated Organic Compounds as Radiopaque Media

Abstract

The general properties of X-ray contrast media are discussed with particular reference to the use of iodinated organic compounds in cholecystography and urography. The development of test procedures for the evaluation of radiopaques for X-ray visualization of the gallbladder and the upper urinary tract is described. Relative oral cholecystographic activity, from most to least active, was observed in the cat as follows: iopanoic acid, iophenoxic acid, iodoalphionic acid, and iodophthalein, in agreement with the relative order of activity reorted in the literature for these compounds in man. Diatrizoate sodium was found o produce earlier and better X-ray visualization of the uper urinary tract in the rabbit with less than half the systemic toxicity observed wig iodopyracet. The acute intravenous toxicity of diatrizoate sodium in the mouse, rat, rabbit, cat, and dog was found to be approximately half as great as that observed for iodopyracet, sodium iodomethamate, or sodium acetrizoate. An iodinated aromatic nucleus, to provide radiopacity, was found to be common to both cholecystographic and urographic media. The cholecystographic medium required a “transport mechanism” consisting of an alkanoic acid side chain containing 6 to 7 carions with 2 iodines in the aromatic nucleus and 5 carbons with 3 iodines in the radiopaque portion of the molecule. The urographic contrast medium required a carboxyl group to provide high water solubility and could contain an alkanoic acid chain with no more than three carbons.