DIPHTHERIA ANTITOXIN. 405 



For prophylaxis from 500 to 1,000 units are 

 generally recommended,, although some foreign 

 authorities give only 250 units. Rarely, individ- 

 uals who have received such treatment develop 

 diphtheria within twenty-four hours after the in- 

 jection. In these cases it is probable that infec- 

 tion has already occurred and symptoms appear 

 before the antitoxin is thoroughly distributed. 

 Naturally one may contract diphtheria after the 

 antitoxin is eliminated. 



For curative purposes the amount actually re- 

 quired depends on the virulence of the infection 

 and the duration of the disease. Inasmuch as the 

 virulence may not be known accurately, what ap- 

 pears to be an excess of antitoxin is always de- 

 manded. Having in mind the average dose of 

 3,000 units recommended by the recent edition of 

 the United States Pharmacopeia, the physician 

 must be guided by the conditions in the individ- 

 ual case. Less than 2,000 units are rarely indi- 

 cated, and as many as 10,000 and 14,000 units 

 may be given without detriment to the patient. 

 There should be no hesitation about repeating a 

 dose within twenty-four hours in the absence of 

 distinct improvement. 



Ransom and Knorr state that if the antitoxin 

 is given intravenously, which may be done without 

 danger, the action of the serum is about eight 

 hours earlier than when given subcutaneously. In 

 severe and in late cases it is advisable to use this 

 method of introduction, the serum first being 

 warmed to the temperature of the body. It should 

 be remembered, however, that the dangers of ana- 

 phylactic symptoms are much increased by intra- 

 venous injection. 



