THE DIGITALIS-LIKE PRINCIPLES OF CALOTROPIS COMPARED WITH OTHER CARDIAC SUBSTANCES

¹ The Lilly Research Laboratories, Eli Lilly and Company, Indianapolis
² Biometrician, Connecticut and Storm Agricultural Experiment Stations, New Haven

1. Of the three digitalis-like principles of Calotropis, their potencies relative to each other and to ouabain were in the following order when tested in parallel:

All differences were significant except that between calotropin and calotoxin in cats.

2. By simultaneous comparison of the above 4 drugs with 8 other cardiac principles in etherized cats, their potencies in anhydrous form r lative to ouabain were convallotoxin 112, ouabain 100, -antiarin 90, -an iarin 87, cymarin 86, calotropin 83, coumingine HCl 78, calotoxin 76, emicy^tmarin 63, bufotalin 61, uscharin 58, and periplocymarin 55. Differences between pairs in the above series that are less than 18 per cent of the smaller potency cannot be considered significant.

3. For 10 of the above drugs, the median lethal dose had also been determined individually over a period of several years and in four cases the new values differed significantly from the earlier determinations, demonstrating the importance of parallel tests with group standards in experiments on the toxicity of cardiac substances to cats.

4. The lethal dose in cats showed a closer relation to the size of the heart, in terms of the power of its fresh weight, than to the weight of the body, so that comparisons of drugs corrected for size of heart were the more precise and have been quoted in the summary. Due to the high correlation between heart weight and body weight, relative potencies determined by both procedures agreed within a few per cent.

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