Experimental studies on the pharmacokinetics and toxicity of 5-aminosalicylic acid-O-sulfate following local and systemic application.

5-Aminosalicylic acid-O-sulfate (5-ASA sulfate), a new agent for the treatment of ulcerative colitis and Crohn's disease of the large intestine, was investigated for its pharmacokinetic and toxicological properties, following local and systemic application. 5-ASA sulfate can be considered as a non-toxic agent after single oral intake in rats (14-day LD50 > 6000 mg/kg b.w.). Oral application of 2500 mg 5-ASA sulfate/kg b.w./d for 28 days to rats resulted in significantly increased body weight gain and food and water consumption. Alanine aminotransferase and alkaline phosphatase values were elevated in high-dosed (2500 mg/kg b.w./d p.o.) males. Relative liver weights were significantly increased in high-dosed males and females and the macroscopical inspection revealed thickened liver margins. The no-effect level following 28 days of oral application to rats was determined as 500 mg 5-ASA sulfate/kg b.w./d. In acute local tolerance studies in rabbits, 5-ASA sulfate is rated as non-irritant to the skin and the eye. After a single oral administration of 1800 mg 5-ASA sulfate to 5 healthy human test subjects, 5-ASA sulfate was almost completely metabolized by all test subjects within 3 days; mean urinary and faecal excretion of unchanged 5-ASA sulfate amounted to only 6.7% of the administered dose. A high faecal excretion of the active metabolite 5-aminosalicylic acid (5-ASA) (21.2% of the administered dose) and a low urinary excretion (1.4% of the administered dose) were observed.