The metabolism of sulphapyridine containing radioactive sulphur in the rabbit.

This paper records a further stage in the attempt to draw up a balance sheet for the fate ofa single dose of sulphapyridine in the rabbit. Bray, Neale & Thorpe (1946) found that a considerable proportion ofa dose of sulphapyridine could not be accounted for in rabbit urine by methods of estimation based upon the diazo reaction, especially at higher dose levels (0-5--0 g./kg.). We were unable significantly to improve the recovery by analysis of the faeces or contents of the alimentary canal. An increased excretion of inorganic sulphate in approximately onethird of the animals roughly corresponding to the missing sulphapyridine suggested the possibility of formation of a metabolite in which the amino group of sulphapyridine has been eliminated, although we have so far failed to isolate such a compound. There is no appreciable retention of the drug in the tissues.