Stability of disodium azodisalicylate (olsalazine) and metabolites in urine and faeces stored at different temperatures.

Methods: The stability of disodium azodisalicylate, 5-aminosalicylic acid and acetyl-5-aminosalicylic acid dissolved in distilled water and in urine or mixed with faeces to which HgCl2 was added, was studied at -20 degrees C, 4 degrees C and room temperature.
Results: In water, no marked differences were found between the three storage regimens. In urine, disodium azodisalicylate and acetyl-5-aminosalicylic acid were stable, while the 5-ASA concentration decreased when stored at 4 degrees C and room temperature. In faeces stored during seven days, a marked decrease in 5-aminosalicylic acid concentration to about zero was found when it was kept at 4 degrees C and room temperature. No marked change in the concentration of disodium azodisalicylate and 5-aminosalicylic acid added to the faeces-HgCl2-mixtures appeared.