AUGUST 19, 1921 ALSBERG : PHYSIOLOGICAL CHEMISTRY 335 



properties of drugs and their specific manner of action. ^^ 



As no sharp line can be drawn between chemistry and physics so 

 these aims of the synthetic chemist in the field of chemo-therapy can 

 not be separated sharply. The attainment of one aim is very apt to 

 bring the other in its train. Thus the rate of action of a drug may be 

 accelerated or retarded by merely changing its solubility. The more 

 soluble it is the more rapidly may it be absorbed and the more intense 

 will be its action, since, obviously, the more rapidly it floods the body 

 the more toxic will it be. At the same time its action is likely to be 

 more evanescent because just as it will be more rapidly absorbed so 

 it is apt to be more rapidly eliminated. The less soluble it is the 

 more slowly will it be absorbed and the milder and more continuous 

 is apt to be its action. Moreover, at the same time, changing its 

 solubility may change the site of action of a drug as when it is rendered 

 insoluble in the stomach but soluble in the intestines. Such an example 

 is the tannate of an alkaloid. These tannates are insoluble in the 

 stomach, but soluble in the intestines. Therefore not merely is their 

 rate of action modified but the action itself may not begin until the 

 drug reaches the intestines. The rate, the intensity, as well as the 

 site of action have been modified by the mere change in solubility. 



Similar changes in the action of drugs can be brought about by 

 making derivatives that are inactive in themselves but are decomposed 

 somewhere in the body setting the active principle free. By such 

 means it is possible to retard the rate and also to change the site of 

 action. Salol, a condensation product of phenol and salicylic acid, 

 is a good example of this sort. It passes through the acid stomach 

 but is esterified in the alkaline intestines with the gradual liberation 

 of its component drugs. Thus they act slowly and less intensely, 

 exerting local antiseptic action in the intestines and, after gradual 

 absorption, continuous systemic action. A similar result is accom- 

 plished in the administration of inorganic substances if converted into 

 un-ionized organic compounds. Such compounds may reach the 

 tissues before they are decomposed, exerting their action at the site of 

 decomposition. Salvarsan and its congeners are examples of this 

 kind. They are organic compounds of arsenic which are but slowly 

 decomposed within the tissues. By their use it is possible to keep the 

 body continuously under the influence of arsenic without serious toxic 

 symptoms. No doubt a part of the value of salvarsan is due to the 



'* S. Fraenkel. Die Arzneimittelsynthese auf Grundlage der Beziehungen zwischen 

 chemischen Aufbau und Wirkung. (J. Springer, Beriin, 1912.) 



