374 VEGETABLE DRUGS 



Caffeina Citrata. Citrated Caffeine. (U. S. P.) 



Derivation, — Dissolve citric acid (50) in hot, .distilled 

 water; add caffeine (50) and evaporate the resulting solu- 

 tion, on a water bath, to dryness, constantly stirring towards 

 the end of the operation. Reduce the product to a fine 

 powder and transfer it to well-closed bottles. 



Properties. — A white powder, odorless, having a purely 

 acid taste and acid reaction. One part of citrated caffeine 

 forms a clear, syrupy solution, with about 3 parts of water. 

 Upon dilution with water this yields a white precipitate 

 (caffeine), which redissolves when about 25 parts of water 

 have been added. It is also soluble in a mixture of two 

 volumes of chloroform and 1 volume of ether. 



i>o.se.--H., gr.xv.-xxx. (1.-2.); D.,gr.i.-vi. (.06-.36). 



Action Internal, — Caffeine has no particular action upon 

 the digestive tract, except in large quantities, when it may 

 cause gastro-intestinal irritation. The effect of caffeine and 

 raw coffee is identical, but when the latter is roasted, aroma- 

 tic oils, or an empyreumatic oil, are developed (caffeone). 

 It is impossible to separate completely the action of caffeine 

 from caffeone in boiled coffee. Recent investigations appear 

 to show that the oil (caffeone), of which there is from one to 

 one-half drachm in a cup of the beverage, has no physiolo- 

 gical action except to disturb digestion and cause bilious- 

 ness. This result is not in accord with the general belief, 

 and it is probable that caffeone possesses a transient action 

 in stimulating intestinal peristalsis, the cerebral functions, 

 and in lessening vascular tension. 



Circulation. — Caffeine increases blood pressure by mak- 

 ing the heart beat more forcibly and rapidly. The systolic 

 contractions are longer and stronger. Experimental evi- 

 dence concerning the physiological details of its action upon 

 the heart is contradictory. The vasomotor centres are not 

 influenced by the drug except in poisoning, when both the 

 heart muscle and vasomotor system are depressed, and the 

 heart stops in diastole after cessation of respiration. 



