Bioavailability of 5-aminosalicyclic acid from slow release 5-aminosalicyclic acid drug and sulfasalazine in normal children.

The bioavailability of a controlled release 5-aminosalicyclic acid preparation (Pentasa) was investigated in nine healthy children after a medication period of six days (1000 mg/day) and compared with sulfasalazine (Salazopyrin) (2000 mg/day). The local bioavailability in the distal gut lumen, reflected by the 5-aminosalicylic acid concentration in the fecal water, showed comparable values after Pentasa (4.44 mmol/liter) and Salazopyrin (6.25 mmol/liter). The concentration of N-acetyl-5-ASA was significantly higher after Pentasa, reflecting the more proximal release of 5-aminosalicyclic acid compared with Salazopyrin. No relation was found between the 5-aminosalicylic acid fecal water concentration water concentration and the 5-aminosalicylic acid dose per kilogram of body weight. The urinary excretion of 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid was higher after Pentasa than after Salazopyrin (32% vs 25%). Dose interval plasma concentration curves showed low values after both preparations. Based on the concept that the fecal water concentration is decisive for the efficacy of 5-aminosalicylic acid in distal inflammatory bowel disease, Pentasa treatment offers a relevant alternative in cases of Salazopyrin intolerance or allergy in children. The higher systemic bioavailability from Pentasa warrants monitoring of the renal function.