18 GENERAL ACTIONS OF DRUGS 



The alkaline carbonates allay pain by means of the carbonic 

 dioxide set free in their decomposition in the digestive tract, 

 and the antacids are also beneficial in dissolving an exces- 

 sive secretion of mucus in catarrhal conditions of the alimen- 

 tary canal. 



The antacids are synonymous with alkalies, with the 

 exception of the neutral vegetable salts — acetates, citrates 

 and tartrates — of potassium and sodium, which are some- 

 times classed under this head. These do not alkalize the 

 contents of the stomach, but nevertheless are broken up in 

 the body and transformed into carbonates and thus render 

 the urine more alkaline during their elimination. Among 

 those included in the following list the sodium compounds 

 are much less active in alkalizing the urine than the potas- 

 sium salts. Sodium bicarbonate is in most frequent use in 

 digestive disorders, but ammonium carbonate is particularly 

 appropriate in flatulence, because it possesses more power 

 in stimulating peristaltic action and expelling flatus. 



ANTACID.S. 



Sodium carbonate Ammonium carbonate 



Sodium bicarbonate Magnesia 



Potassium carbonate Magnesium carbonate 



Potassium bicarbonate Calcium carbonate (chalk) 



Solution of potash Solution of lime (lime water) 

 Ammonia 



Acids. — Contrary to accepted ideas, Pawlow's experi- 

 ments show that mineral acids directly stimulate the secre- 

 tion of acid in the stomach, and, indirectly, the secretions 

 of the intestines, liver and pancreas. In the latter part of 

 gastric digestion, the acid product of the first part of diges- 

 tion acts on the mucosa to cause the formation of a body 

 called secretin. This is absorbed into the blood and stimu- 

 lates the activity of all the gastric glands. In the intestines, 

 acid chyme likewise leads to secretin formation, 'which like- 

 wise is absorbed and stimulates the secretion of the intes- 

 tines, liver and pancreas. 



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