A NEW method for evaluating the toxicity of roentgen contrast media

Transcription

1 EVALUATION OF ROENTGEN CONTRAST AGENTS USED IN CEREBRAL ARTERIOGRAPHY II. APPLICATION OF A NEW METHOD* G. T. TINDALL, M.D., P. D. KENAN, B.S., R. L. PHILLIPS, M.D., G. MARGOLIS, M.D., AND K. S. GRIMSON, M.D. Departments of Pathology and Surgery, and the Division of Neurosurgery, Duke University School of Medicine, Durham, North Carolina (Received for publication April 11, 1957) A NEW method for evaluating the toxicity of roentgen contrast media has been described in the preceding paper. 4 This testing method, which employs the spinal cord of the (log as the site of the test, uses the following criteria as indices of toxicity: the immediate convulsive effect, the residual neurological deficit, and the resultant anatomic changes in the spinal cord. The application of this method to a comparative study of five contrast media is presented in the present report. EXPERIMENTAL The contrast media tested in this study included Diodrast, Hypaque, Urokon, Miokon, and Renografin.t The structural formula of each of these agents is shown in Fig. 1. The basic molecule of Hypaque and Renografin is identical, the only difference between these two agents being the relative proportion of sodium and methylglucamine diatrizoate contained in each. '~,6 The methylglucamine radical has been added to these compounds in order to increase their solubility. 6 It is also present in the 90 per cent solution of Miokon, or sodium diprotrizoate. The absolute per cent of the sodium and methylglucamine salts in Hypaque, r Renografin} and Miokon is shown in Table 1. The per cent concentration of Hypaque and Niiokon used in the present study was obtained by mixing equal volumes of the and 90 per cent solutions. The per cent concentration of Renografin was obtained by mixing equal parts of the 60 and 85 per cent solutions and adding an appropriate quantity of distilled water. These tests followed the methods presented in detail in the preceding paper. 4 The basic plan of the study called first for an evaluation of each agent in a per cent concentration at doses of 1 cc. per kg. When a compound was found to be highly toxic the total dose at this concentration was halved, or the agent was tested in progressively decreasing concentrations, holding the total volume of the injection at 1 cc. per kg., until a non- * This study was supported by a research grant (B 110~2 and G 869) from the National Institutes of Health and by a research grant from the National Paraplegic Foundation. The contrast media were kindly furnished in generous quantities by the following: Winthrop Laboratories, Inc., New York, N.Y. (Diodrast and Hypaque) ; Mallinckrodt Chemical Works, St. Louis, Missouri (Urokon and Miokon); and E. R. Squibb and Sons, New York, N.Y. (Renografin). 37

2 38 G. T. TINDALL ET AL. FIG. 1. Structural formula of contrast media used in this study. TABLE 1 Proportion of sodium and methylglucamine salts in Hypaque, Renografin, and Miokon Contrast Agent Concentration Per Cent w/v Absolute Per Cent (w/v) of Sodium and Methylglucamine Salt in Each Agent Sodium Salt Methylglucamine Salt Hypaque (diatrizoate) Renografin (diatrizoate) ~ Miokon (diprotrizoate)

3 EVALUATION OF ROENTGEN ON IRASI AGENTS--II 89 TABLE Summary of evaluation tests of five roentgen eontra,s't agents" in 79 dogs Agent ])ose, ee./kg. Concentration (Per Cent) of Agent and Number of Animals Tested 80 Urokon ,* Diodrast 5 ~.0 5 Hypaque 5 ~ Miokon 5 ~ 6 Renografin 1,0 * 8 animals injected in prone position. toxic level was reached. When a compound was found to be relatively innocuous the dose was doubled or trebled until a definite toxic level of the concentrated ( per cent) agent was found. A summary of these evaluation studies is presented in Table ~, which also lists a few other variations of the testing procedure. All compounds were kept sealed and protected from light until ready for injection. Various factors such as the care and handling of the animals, the temperature of the injected media, and the operative technic were closely controlled. RESULTS Urokon. The tests of this agent, evaluated in 33 dogs, are smnmarized in Table 3. In a per cent concentration this compound exerted a severe toxic effect at both and cc. per kg. doses. When this volume dose was kept at 1 ce. per kg. and the concentration of the agent was reduced, severe toxic effects were encountered in e of 5 animals injected with per cent solution, and it was not until the concentration was reduced to per cent that a significant reduction in toxicity was consistently observed. The animals receiving the per cent concentration in a 1 cc. per kg. dosage showed no toxic effects. The influence of posture upon the toxic action of this agent is illustrated by the protective effect in 8 dogs injected in the prone position. Diodrast. A summary of the tests on 10 dogs with this agent is presented in Table 4. In doses of 1 ee. per kg. the per cent concentration of this medium produced a low order of toxic effect, manifested by a convulsive response and a low-grade anatomic lesion, but without recognizable

4 G. T. TINDALL ET AL. TABLE 3 Summary of toxic effects produced by retrograde intra-aortic injection of Urokon (33 dogs) Animal Cone. Dosage, Convulsive Neurologic Anatomic Number Position % cc./kg. Effect Impairment Lesion s ~7 ~8 ~o O 7O 7O 7O 4O 4O TABLE 4 Summary of toxic effects produced by retrograde intra-aortic injection of Diodrast 'with animals in supine position (10 dogs) Animal Cone. Dose, Convulsive Neurologic Anatomic Number % ee./kg. Effect Impairment Lesion (Grade) o~ 48 ~ IIOIl~

5 EVALUATION OF ROENTGEN TABLE CONTRAST AGENTS--II 41 5 Summary of toxic effects produced by retrograde intra-aortic injection of Miokon with animals in supine position (11 dogs) Animal Cone. Dosage, Convulsive Neurologic Number % ce./kg. Effect Impairment ~.0 Anatomic Lesion (Grade) severe neurologic impairment. At r ce. per kg. the per cent preparation produced a neurologic impairment, without a significant increase in the convulsive action or the grade of anatomic lesion. Miokon. The results of the tests on 11 dogs with this substance are summarized in Table 5. At 1 cc. per kg. the per cent solution produced inconsistent and borderline toxic effects, without recognizable neurologic impairment in the injured animals. At ~ cc. per kg. the per cent concentration was consistently toxic, but severe injury was observed in but 1 of 6 animals. In addition to parenchymal injury a degeneration of isolated fibers in the spinal nerve roots of the lumbosacral cord was demonstrated in 8 dogs. The parenchymal injury was the predominant lesion in these animals, however. TABLE 6 Summary of toxic effects produced by retrograde intra-aortic injection of Hypaque with animals in supine position (15 dogs) Animal Number Cone. % Dosage, ce./kg ~ !. 0 ~.0 ~.0 i.o i.o Convulsive Effect llone Neurologic hnpairment Anatomic Lesion (Grade)

6 4~ G. T. TINDALL ET AL. TABLE 7 Summary of toxic effects produced by retrograde intra-aortic injection of Renografin with animals in supine position (10 dogs) Animal Colic. Dosage, Convulsive Neurologie Anatomic Number % ce./kg. Effect Impairment Lesion (Grade) Bolle llone Hypaque. The results of tests on 15 dogs with this compound are shown in Table 6. The 1 cc. per kg. dose of the per cent concentration produced no residual toxic effects. When the dose of this concentration was doubled and trebled minimal toxic effects were observed, without recognizable functional impairment in the injured animals. Rare degenerating fibers in the spinal nerve roots were noted in 9 dogs. In all but one animal (dog No. 65), these were the only anatomic changes noted. Renografin. The tests of this agent in 10 animals are summarized in Table 7. At both 1 cc. and 3 cc. per kg. dose levels the per cent concentration produced a convulsive response and a grade 1 anatomic lesion in most animals tested, without recognizable residual neurologic impairment. Scattered degenerating spinal root fibers were found in 3 dogs. In this series, however, parenchymal lesions were the predominant feature. TABLE 8 Summary of toxic effects produced by retrograde intra-aortic "injection of contrast media (includes dogs in supine position only) Agent Urokon Diodrast Miokon Hypaque ~0 Renografin I Criteria of Injury and Number of Animals Number Immediate Convulsive Neurologic Impairment I Anatomic Lesion Ani- Response (Grade) (Grade) I (Grade) nmls! I Mod S... IS... 0 I1]~1 3 4 ]5 ono I I t I ~11 3.] T, 11::1 3 3 ] ~ 4

7 EVALUATION OF ROENTGEN CONTRAST AGENTS--II 43 A composite summary of the tests of all these contrast agents in the per cent concentration made with the animals in the supine position is presented in Table 8. Urokon is clearly of a different order of toxicity than any of these agents. At one-quarter and one-sixth the dosage level of the other media that produced minimal to changes, severe toxic effects were still encountered with Urokon. Hypaque and Renografin are the least toxic, with Diodrast and Miokon occupying an intermediate position in the order of toxicity. DISCUSSION The lack of significant differences between the toxicity of Hypaque and Renografin is not surprising in view of the fact that the only difference in the higher concentration of the two agents lies in the differing proportions of sodium and methylglueamine salts (Table 1). Urokon, or sodium acetrizoate, is quite similar to the basic Hypaque and Renografin molecule-- sodimn diatrizoate--the only difference being the absence of an additional acetylamino group in the former (Fig. 1). Our studies demonstrate adequately that the addition of the acetylamino group to the acetrizoate molecule reduces strikingly its local toxic effect on the spinal cord. This finding is in complete agreement with the observations of Langecker et al. 2 and Moore and others 5 with regard to the general toxicity of these compounds. The conclusions drawn from this study regarding the relative toxic effects of various contrast media on the spinal cord of the dog are in agreement with previous studies in which the brain was used as the testing site. Workers at Winthrop Laboratories 6 studied the relative toxic effects of Urokon, Hypaque, and Diodrast, using injury to the blood-brain barrier of the rabbit as their principal criterion of a toxic action. Using enornmus test doses (~5 cc. at a rate of ~2 cc. per see.), they found that the order of increasing toxicity was Hypaque, Diodrast and Urokon. Bloor, Wrenn and Margolis I using electroencephalographic changes, barrier disturbances, and early anatomical changes as the criteria of injury, found,' per cent Urokon to be approximately four times as toxic on the rabbit brain as 85 per Cent Diodrast. Whiteleather and DeSaussure 7 compared the toxic effect of per cent Hypaque, 35 per cent Diodrast, and and per cent Urokon on the brain of the dog, using barrier disturbances, respiratory effects, and the immediate convulsive response as indicators of toxicity. Significant reactions or evidence of disturbances of permeability did not occur with 35 per cent Diodrast or per cent Hypaque even when amounts as high as cc. of either agent were given in a single injection. These workers, however, did not compare directly equal concentrations of these two agents. Thirty per cent Urokon caused little respiratory or convulsive response, but did produce definite injury in amounts of : cc. in single injections. The injection of per cent Urokon, even in doses of 10 cc., resulted in convulsions and impairment of the blood-brain barrier in various degrees. In our studies there was an excellent correlation of the three criteria of injury in the severe toxic reactions (Table 8). But, in the lesser grades of

8 44 G. T. TINDALL ET AL. injury this correlation was not so exact, the anatomic lesion being a far better indicator of a toxic effect than the convulsive reaction or the residual neurologic deficit. SUMMARY 1. A new method which employs the spinal cord of the dog as the testing site and which uses as criteria of injury the immediate convulsive response, the residual neurological deficit, and the resultant anatomic cord lesions has been used to test the toxicity of five contrast media designed for use in artcriography. 2. Of the criteria of injury, the anatomic lesions of the cord proved to be the most sensitive, determinate, and quantitative index of toxicity. 3. The tests showed that Urokon was the most toxic agent tested. Renografin and Hypaque were equal with respect to toxicity and were less toxic than the other media. Diodrast and Miokon were intermediate in toxicity between the other agents and were about equal to each other in this respect. REFERENCES 1. BLooR, B. M., WRENN, F. R., JR., and MARGOLm, G. An experimental evaluation of certain contrast media used for cerebral angiography. Electroencephalographic and histopathological correlations. J. Neurosurg., 1951, 8: ~. LANGECKER, H., HARWART, A. and JUNKMANN, K. 3,5-Diacetylamino-~,4,6-trijodbenzoes~ture als RSntgenkontrastmittel. Arch. exp. Path. Pharmak., 1954, 222: LUND, M. It. The Squibb Institute for Medical Research. Personal communication. 4. MARGOLIS, G., TINDALL, G. T., PHILLIPS, R. L., KENAN, P. D., and GRIMSON, K. S. Evaluation of roentgen contrast agents used in cerebral arteriography. I. A simple screening method. J. Neurosurg., 1958, 15: MOORE, C., CLOKE, B., HOPPE, J. O., and LAaSEN, A.A. Iodinated 3,5-diaminobenzoic acid derivatives. American Chemical Society, Division of Medicinal Chemistry. Abstracts of papers, l~6th meeting, New York, Sept. 1~-17, 1954, pp. lln-i~n. 6. SAYERS, R.V. Department of Medical Research, Winthrop Laboratories. Personal communication. 7. WHITE]hEATHER, J. E., and DESAUSSURE, R.L. Experience with a new contrast medium (Hypaque) for cerebral angiography. Radiology, 5956, 67: