Chapter VII 



THE PHARMACOLOGY OF EPINEPHRINE 



The pharmacology of epinephrine has been studied very 

 thoroughly, the wide variety of its actions having invited at- 

 tention from numerous investigators. Some of the discrepan- 

 cies between the work of different authors may be attributed 

 to their failure to appreciate that, not only quantitatively but 

 qualitatively as well, the results obtained from epinephrine 

 will depend upon the dosages employed. Most authors have 

 been content to use commercially available epinephrine solu- 

 tions instead of the pure crystalline material for their work, 

 thus disregarding the effects of the acid and chloretone which 

 these solutions contain. Chloretone exerts particularly poi- 

 sonous effects on smooth muscle. 639 



Almost without exception the effect of injecting epinephrine 

 is the same as stimulating the sympathetic nerves and hence 

 epinephrine is spoken of as a sympathomimetic substance. 

 Epinephrine affects practically all tissues which are supplied 

 with nerves of the sympathetic system. On the other hand, 

 its action on tissues not innervated by the sympathetic is slight. 

 Thus, contrasted to the marked activity which epinephrine 

 exerts on blood vessels, it has no action on the placental vessels 

 which are not under sympathetic control. In the embryo, 

 tissues are not affected until they have become innervated by 

 sympathetic fibers. However, epinephrine is said to affect the 

 heart of the embryo fish and the blood vessels of the chick 

 embryo before their innervation. 639 In the chick's amnion, 

 likewise, although not known to contain any nerves, the rhyth- 

 mic contractions of the unstriped muscle are inhibited by epi- 

 nephrine. 379 The action of epinephrine, however, is not upon 

 the nerves or their endings, for sectioning the nerves not only 



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