Abstract

1. Quinine administered orally with sulfapyridine to rats increased the total amount of sulfapyridine absorbed and excreted in the urine. The maximal increase was produced by the largest dose of quinine and, using average values, amounted to 44 per cent.

2. The increase in the urinary excretion of total sulfapyridine represented principally an increase in the acetylsulfapyridine. The largest dose of quinine produced an average increase of 96 per cent in the excretion of acetylsulfapyridine. This effect was not accompanied by an increase in the volume of urine.

3. Quinine depressed the free sulfapyridine in the urine. The maximal decrease observed was 33 per cent.

4. Atabrine substituted for quinine produced no comparable effect.