108 VASODILATORS 



culation. If those of the kidneys are relatively more dilated, 

 diuresis takes place. 



Differences in Members and Administration. The members 

 of this group differ mainly in rapidity and persistence of action. 

 Amyl nitrite, inhaled, is the most rapid and least persistent. It will 

 produce action in from 10 to 15 seconds which will last about 3 

 minutes. Nitroglycerin may be given per os or hypodermically and 

 is almost immediately absorbed. The fall in blood pressure staits in 

 % to 3 minutes, reaches the maximum in 5 to 15 minutes, and dis- 

 appears in % to 1 hour. Sodium nitrite is to be given per os and 

 is less rapidly absorbed. Its action starts in from 5 to 30 minutes, 

 reaches its maximum in 20 to 80 minutes and is completely over in 



1 to 2 hours. Erythrol tetranitrite is also given per os. Its action 

 is still slower. The fall in pressure begins in from 5 to 30 minutes, 

 reaches its maximum in from /4 to 2 hours later and disappears in 

 from 2 to 5 hours. 



Mannitol has about the same action as erythrol. 



Therapeutics. The nitrites are used almost entirely to relax 

 constricted arteries and bronchi. The uses may be summarized as 

 follows : 



1. To relieve excessive resistance to the work of the heart, as in 

 arteriosclerosis. 



2. Antispasmodic: Inhalations of amyl nitrite may be of ser- 

 vice in the spasms of epilepsy, tetanus and strychnine poison and 

 to relieve asthmatic seizures in the dog. 



3. They have some indication to lower blood pressure in hemor- 

 rhage, although one would expect to counteract any beneficial action 

 by dilatation of the bleeding vessels. 



4. In toxic rise of blood pressure; poisoning from digitalis, 

 strychnine, barium and in lead colic. 



5. As a diuretic and diaphoretic in colds and mild fevers. Spirits 

 of nitrous ether. 



6. Amyl nitrite may be useful to overcome chloroform poisoning 

 on the theory that it overcomes resistance and saves an exceedingly 

 weak heart. According to Miihlberg and Kramer, it is effective in 

 preventing the stoppage of the heart in the first and second stages 

 of chloroform and ether anesthesia, although chloroform containing 



2 per cent, of amyl nitrite is more toxic than when used alone. 



The second and fourth uses are the only ones of importance in 

 veterinary medicine. 



5 Spiritus Glycerylis Nitratis ill xv 



Glycerin! 3 ijss 



Aquse DestillatEe S iij 



M. Ft. Solutio. 



Sig. Teaspoonful three times daily for a dog with pulmonary 

 emphysema. 



