Abstract
Shortly after the synthesis of epinephrine, studies were carried out on the comparative actions of the synthetic and the natural substances. Chemically the artificial base was identical with the natural substance in all respects except that it was optically inactive while natural epinephrine is levorotatory. Beberfeld 1 studied the comparative actions of racemic synthetic epinephrine and the levorotatory natural base in rabbits and concluded that they were exactly equivalent. Cushny 2 found in dogs that the natural epinephrine was twice as active on the blood pressure as the synthetic isomer and concluded that the dextrorotatory substance was devoid of action on the blood vessels. Since 1908 when the dextro-component became available, several observers have reported on the comparative activities of the isomers. Practically all agree that the d-isomer has a relatively weak action. The following ratios of activity have been reported in dogs: 1:12 to 1 :15, by Cushny 3 ; 1:15 by Abderhalden and Müller 4 ; 1:15 to 1:20 by Tiffeneau 5 ; and 1:30 to 1:40 by 'Fromherz. 6 Richaud, 7 however, concluded that levo-epinephrine was only slightly more active than the racemic form so that in therapy the synthetic substance should give approximately the same effect. His method, however, for estimating quantitative reactions is not entirely acceptable. In rabbits Launoy and Menguy 8 found a ratio of activity of 1 :30, while in cats Tainter 9 reported a ratio of 1 :20.
The method which has been used almost exclusively for the study of comparative actions of these isomers has been the pressor response in experimental animals. Cushny 3 has pointed out that the comparative activities of optical isomers may not be the same on different organs.
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