Therapeutic Efficiency of Arsphenamine 



57 



is also lowered, the ratio of the minimum lethal dose of arsphena- 

 mine to that of gelatin-arsphenamine being as 10 is to 14. 



The relative therapeutic action of arsphenamine and gelatin- 

 arsphenamine was next examined. A priori it may be argued 

 that the gelatin will "protect" the parasite in the same manner 

 as it does the blood cells and tissues of the host. On the other 

 hand, our experiments have shown that the gelatin-arsphenamine 

 is more slowly excreted, and that therefore a higher concentra- 

 tion of it persists in the blood stream and tissues than after the 

 administration of an equal amount of arsphenamine. The thera- 

 peutic efficiency of gelatin-arsphenamine would be the resultant 

 of these two opposing factors. 



In testing the therapeutic efficiency we have followed the 

 method described by Voegtlm 4 . Trypanosoma Brucei were used. 

 Rats showing from 150,000 to 300,000 trypanosomes per c.mm. 

 of blood were given increasing doses of the two substances in- 

 travenously. The blood was examined after 24 hours for the 

 presence of parasites and every day for 3 weeks. 



The result of 50 experiments may be summarized as follows : 

 Arsphenamine and gelatin-arsphenamine have the same minimum 

 effective dose of 10 mg. per kilo. Such a dose frees the blood 

 stream of parasites in 24 hours. The minimum sterilizing 4 dose 5 

 which prevents relapses for 21 days is also the same with the two 

 drugs, 20 mg. per kilo. 



The chart compares these findings to the results of similar 

 experiments of Voegtlin and of Schamberg, Kolmer and Raiziss 

 with arsphenamine and neo-arsphenamine. It will be noted in 

 comparing the minimum effective doses that the ratio of the in- 

 minimum lethal dose 



dices of therapeutic efficiency, — , of 



minimum effective dose 



gelatin-arsphenamine is 1.4 times greater than that of arsphena- 

 mine. As will be seen under Voegtlin's findings, this figure is 

 slightly larger than the corresponding ratio of neo-arsphenamine 

 to arsphenamine. Gram for gram, however, gelatin-arsphena- 

 mine is twice as effective as neo-arsphenamine and equally ef- 

 fective as arsphenamine. 



* Public Health Reports, 1922, xxxvii, 1627. 

 5 Schamberg, Kolmer and Raiziss, Amer. Journ. Med. Sciences, 1920, clx, 25. 



