Abstract

The metabolism of salicylazosulphapyridine was studied in 16 patients with ulcerative colitis admitted to hospital. The acetylator phenotype was determined on admission. The mean serum concentration (μg/ml) (at steady state eight ± two days in patients responding to treatment) of SASP, total SP, and 5-ASA were 18·7 ± 12·8; 53·7 ± 23·1; and 1 ± 0·9 for slow acetylators and 17·6 ± 7·1; 31 ± 9·0 and 1 ± 0·9 for fast acetylators respectively. Twenty-four hour urinary excretion of SASP, total SP, and 5-ASA were 4·6% ± 3·1; 52% ± 9·6 and 22·3 ± 6·7% of the administered dose respectively.

Serum total SP concentration of 20 to 50 μg/ml appeared to coincide with clinical improvement in the absence of any side effects related to salicylazosulphapyridine. No such relationship could be shown with serum SASP, individual metabolites, or 5-aminosalicyclic acid.