The Persistence of Effect of Thevetin

Abstract

Thevetin is a glycoside obtained from the kernels of the “be-still” tree; Thevetia neriifolia (Jussieu) family Apocynaceae. Chen and his associates 1 , 2 , 3 have discussed the bibliography and described the various constituents of these nuts. They have also studied experimentally and clinically the biological potency and characteristic digitalis effect of thevetin. 1 2 3 4 5 6

A limited number of experiments concerned with the persistence of effect of thevetin in the cat has been reported by Chen and Chen, 2 the results of which indicate that the physiological effect of thevetin endures only for a relatively short period of time, approaching ouabain in this respect.

In view of recent observations which we have made on the persistence of effect of several digitalis substances in the pigeon, 7 it was of interest to extend our studies to include thevetin for purposes of comparison. About 130 pigeons were employed in the present observations.

The thevetin∗ was standardized by the intravenous pigeon fatal dose method as described previously. 8 A 1–10,000 thevetin solution was injected into the alar vein of etherized pigeons, 0.5 cc. every 10 minutes. The minimum lethal dose (M.L.D.), i. e., weight of bird under amount of drug, was determined for 24 pigeons. The average M.L.D. was 1.95 mg. per kg. Thevetin was also standardized upon 10 cats according to the technic of Hatcher and Brody 9 and in conformity with experiments of Chen and Chen. 2 The cat unit was 1.0 mg. Chen and Chen 1 originally obtained a slightly higher figure: 1.24 mg., but subsequently, 2 with a more purified product, they found the cat unit to be 0.85 mg. From our studies upon pigeons and cats thevetin appears to be about 1/10 as active as ouabain, U.S.P. XI. Chen and Chen 2 found that purified thevetin was about 1/8 as toxic for frogs, and 1/7 as toxic for cats as ouabain.