144 



BACTERIOLOGICAL CHEMISTRY 



O 



sulpliathiazole (see |)p. 132, J 33) it in probable that the 

 most active of the siilphonamide drugs are already known. 

 Possibilities of more therapeutically useful sulphonamides 

 lie in eliminating the objectionable side effects, toxicity, 

 nausea and so on, and in appropriate modification of 

 solubility and rates of absorption. Thus, although 



o 



3 • 



2 4 6 8 10 12 



pKa 

 Fig. 6 

 sulphadiazine is at the peak of activity, it has a low 

 solubility, especially in acid solution, and tends to 

 crystallize out in the urinary tract when the urine is 

 acid or of small volume, as in hot countries. Sulpha- 

 methazine, 2-sulphanilamido-4:6-dimethylpyridine, is 



