CAFFEINE 395 



Metabolism. — Caffeine increases tissue change and therefore the 

 elimination of urea and carbonic dioxide — contrary to the time honored 

 teaching. 



Toxicology. — Caffeine is a spinal and muscle poison to the frog. 

 Tetanic convulsions occur in the batrachian similar to those produced by 

 strychnine, but there is also muscular rigidity. These phenomena follow 

 the direct stimulation of the spinal motor tract and muscles, and are suc- 

 ceeded by paresis. In man, stimulation of the cerebral cortex occurs, 

 while both stimulation of the brain and cord are observed in the domestic 

 animals. The symptoms of poisoning in dogs, cats and mammals gen- 

 erally, are restlessness, occasionally vomiting in dogs, rapid breathing, 

 primary reduction followed by rise in temperature, clonic or tonic con- 

 vulsions, muscular weakness, and general paresis. Death occurs from 

 heart or respiratory failure. The minimum fatal dose is about 1 gr. to 

 1 lb. of live weight in the cat. 



Administration. — Caffeine and its ordinary salts are decomposed by 

 water and therefore should not be given subcutaneously. The alkaloid is 

 best administered in solution with sodium salicylate, or benzoate, as 

 follows : 



:^ 



Caffeinge. 



Sodii salicylatis aa gr.xxx. 



Aqus destillatse 3ii. 



M. 



S. Give at one dose hypodermically to horse. 

 Ten drops to dog. 



Caffeine sodio-benzoatis 3i. 



Aquae destillatse oil. 



M. 



S. Give at one dose subcutaneously, to horse. 



The soluble citrate may be given internally, but it is not a definite 

 or reliable preparation, and inferior to caffeine, which may be admin- 

 istered in solution with a little citric acid, or as above. 



Uses. — Three indications for the use of caffeine may be deduced 

 from our knowledge of its physiological Action. 1. To stimulate the 

 brain. 2. To stimulate the heart. 3. To cause diuresis. 



1. Its application as a cerebral stimulant is very limited in veteri- 

 nary medicine. It acts thus as an antidote to opium poisoning. One 

 and a half grains of caffeine will save cats poisoned by the minimum 

 fatal dose (gr. 1%) of morphine. 



2. Caffeine possesses particular value in the treatment of dropsy 

 of cardiac origin in dogs, because of its diuretic action, as well as stimu- 

 lant effect upon the heart. The therapeutic indications are not the same 

 as for digitalis, as caffeine differs from digitalis in the following par- 

 ticulars : 



Does not slow the heart. Is not cumulative. 



Does not regulate the heart. Is transient in its effect. 



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