Renal function was not impaired by treatment with 5-aminosalicylic acid in rats and man.

In rat experiments and a clinical trial we have examined the suspected nephrotoxic potential of 5-aminosalicylic acid (5-ASA), the biological active metabolite of sulfasalazine (SZ). Male Wistar rats were treated orally for 4 weeks daily with 30 and 200 mg 5-ASA/kg and 75 and 500 mg SZ/kg. The two renal marker enzymes N-acetyl-beta-D-glucosaminidase (NAG; EC 3.2.1.30), alanineaminopeptidase (AAP; EC 3.4.11.2) and creatinine were monitored in urine. At the end of the experiment rats were sacrificed, the removed kidneys histologically examined and drugs, their metabolites and creatinine measured in plasma and urine. In 9 patients treated chronically for their Crohn's disease with 3 X 0.5 g 5-ASA daily in form of suppositories and an oral preparation urinary excretions of NAG, AAP and serum creatinine were also monitored before and during therapy. Neither the animal experiments nor the observations in patients gave any evidence of nephrotoxic lesions induced by 5-ASA. Thus, our data show that in the doses applied, 5-ASA was devoid of altering renal excretion in rats and man.