Studies on the Pharmacology of Sulfapyridine and Sulfathiazole

It is well known that the absorption of certain sulfanilamide derivatives, such as sulfapyridine and sulfanilyl-sulfanilamide, from the gastrointestinal tract is extremely erratic, so that marked variations in blood concentrations occur in different individuals after unit dosages. Some time ago Marshall and his co-workers¹took issue with the oral L. D.₅₀for sulfapyridine in mice as reported by Wien.²They contended that the latter author used the water insoluble free acid for determining toxicity levels, which is absorbed in so irregular a manner as to render the results unreliable. Marshall showed that when the sodium salt was administered instead of the free acid a definite relationship could be demonstrated between the dosage and the blood level; the L. D.₅₀of sulfapyridine administered as the water soluble sodium salt was approximately oneeighth that of the free acid as obtained by Wien. The freely soluble sulfapyridine sodium is