Absorption, metabolism, and excretion of salicylazosulfapyridine in man

Abstract

Salicylazosulfapyridine (SASP), 4 Gm. daily, was ingested by 9 healthy subfects for 10 days, and the serum concentrations and urinary and fecal excretion of the parent drug and its metabolites were studied. SASP is extensively metabolized by reductive cleavage of the azo linkage, presumably by the action of the gut flora. The sulfapyridine moiety thus formed is subfect to N 4 ‐acetylation or ring hydroxylation followed by confugation to glucuronic acid, or both. The 5‐aminosalicylic acid moiety is N‐acetylated. The steady‐state serum concentrations of the parent drug and its metabolites, obtained by Day 5, for SASP ranged from 4.7 to 45 p.g per milliliter (median 12 p.g per milliliter), for total sulfapyridine metabolites from 37 to 92 p.g per milliliter (median 50 p.g per milliliter), and for total 5‐aminosalicylic acid metabolites to less than 2 p.g per milliliter. The urinary excretion of unchanged SASP ranged from 1.7 to 10 per cent of the dose. About 80 per cent of the dose was excreted in the urine as metabolites of sulfapyridine and one third of the dose was excreted as the metabolite of 5‐aminosalicylic acid. Feces did not contain any SASP, but about 5 per cent of the dose was present as metabolites of sulfapyridine and an unknown amount as metabolites of 5‐aminosalicylic acid.