Experimental Studies of Angio-Conray: A New Angiographic Agent

Cardioangiographic technics involving the use of progressively larger doses of highly concentrated radiopaque agents have clearly indicated the need for new, relatively nontoxic compounds with a high iodine concentration and low viscosity. The development of Angio-Conray,3 which appears to have several distinct advantages in these areas, is a promising step in this direction. An attempt has been made at an evaluation of this new medium in comparison with several other currently popular water-soluble iodinated radiopaque agents, in respect to (a) certain important chemical and physical properties and (b) toxicity when administered intravenously in massive, rapid doses in the dog. Chemical and Physical Properties Angio-Conray is 5-acetamido-N-methyl-2,4,6-triiodoisophthalmic acid and is an isomer of the diatrizoate (Hypaque, Renografin) compounds. It contains 62 per cent iodine. In the commercially available 80 per cent sodium salt solution tested in these studies, there are 48 gm. of iodine per 100 c.c. of solution, the highest iodine content of any currently available organic iodide compound used for angiography. Comparative data concerning the iodine content of other currently available angiographic radiopaque agents are presented in Table I. Studies of viscosity of Angio-Conray over a wide temperature range indicate that it is considerably less viscous than diatrizoate compounds of comparable concentration and iodine content studied at similar temperatures. This comparison is illustrated in Figure 1. These measurements were made with a modified Eckstein, Book and Gregg viscosimeter. The osmolality of this same group of angiographic substances was determined with the Fiske osmometer. Data in Figure 2 indicate the relatively high solubility of the sodium salt of Angio-Conray, which permits a large number of iodine-containing molecules to be dissolved at room temperature without the necessity of utilizing the more viscous methylglucamine salts, as has been necessary in the highly concentrated diatrizoate preparations. Acute Intravenous Toxicity Studies Method: In 30 anesthetized mongrel dogs weighing between 5 and 15 kg. step-wise doses of Angio-Conray were introduced into the vena cava through a 30-inch No. 280 polyethylene catheter attached to a steel syringe and a hand lever injector. In general, the entire dose was administered within two to three seconds. Observations of the blood pressure were monitored with a Statham P-23 Db strain gauge, and lead II of the electrocardiogram was recorded on a Sanborn Twin Viso. Survival, with a return to the blood pressure and electrocardiographic conditions of the control period twenty minutes after the original injection, was considered indicative of tolerance of the procedure. All dogs that succumbed in this study died within the first two minutes following injection.