EPINEPHRINA — EPINEPHRINE 99 



Action. Externally and locally. There is no action upon the 

 unbroken skin, but if it is applied to mucous membranes or raw 

 surfaces, it penetrates sufficiently to stimulate the vasoconstrictor 

 nerve endings of the arterioles at the site of application. This 

 results in a local constriction of the arterioles, vyhich is so marked 

 that the blood is almost completely shut off, and as a consequence, 

 the tissues shrink and become very pale and bloodless, so that any 

 moderate hemorrhage is checked. This local vasoconstriction is 

 greater than from any other drug knovm. This action is produced 

 very quickly and lasts from ten to twenty minutes to two hours, but 

 may be prolonged at will by repeated applications. Vasodilation 

 follows vasoconstriction, so that when the drug is withdrawn or its 

 effects wear off, the arterioles not only relax, but may go beyond their 

 normal tone and there may be a return of the conditions for which 

 it was applied, hemorrhage, etc. The cause of the vasodilation is in 

 controversy. 



Absorption. The drug is not absorbed rapidly enough from the 

 miicous membranes or digestive tract to produce systemic effect, 

 probably on account of the vasoconstriction of the parts with which 

 it comes in contact. 



Subcutaneous tissues. A slight rise of blood pressure often fol- 

 lows the hypodermic administration of adrenaline, but it is not con- 

 stant and cannot be relied upon. 



Intramuscular injection. Enough may be absorbed from deep 

 muscular injections to cause a rise of blood pressure and relax the 

 bronchioles. 



Intravenous injection. When given in small doses intravenously, 

 adrenaline greatly increases blood pressure and slows and strengthens 

 the heart. The increased pressure is largely due to a direct constrict- 

 ing action upon the arterioles but also, to a lesser extent, to stimula- 

 tion of the heart muscle. The pulse is slowed by direct action on the 

 vagus center and also by an indirect action on this center through an 

 increased blood supply. The vasoconstriction is largely peripheral, 

 as can be seen from its local application to mucous membranes or 

 after the central nervous system has been destroyed. 



Respiratory System. Small doses of adrenaline administered 

 hypodermically cause increased depth of the respirations, while 

 larger doses quicken the respirations but render them shallow. 



Muscles. The action of adrenaline varies somewhat upon plain 

 muscle. Thus it has a constricting influence upon the ureter, vas 

 deferens and seminal vesicles in the male, and the uterus and vagina 

 in the female, while it retards movements of the stomach and bowels. 



Glands. Certain glands are stimulated so that there is an in- 

 creased secretion of saliva, tears, bile and bronchial mucus. 



Duration of Action. The period of action of adrenaline is very- 

 short, lasting but a few minutes. There is no characteristic action 



