Comparative bioavailability of 5-aminosalicylic acid from a controlled release preparation and an azo-bond preparation

Aliment Pharmacol Ther. 1994 Jun;8(3):289-94. doi: 10.1111/j.1365-2036.1994.tb00290.x.


Background: Knowledge of the bioavailability of 5-aminosalicylic acid (5-ASA, mesalazine) from the different 5-ASA-containing drugs is important for rational therapy of inflammatory bowel diseases.

Methods: The local and systemic bioavailability of 5-ASA from a controlled release 5-ASA preparation (Pentasa--2, 4 or 6 g/day) was investigated and compared with the azo-bond 5-ASA preparation olsalazine (Dipentum--2 g/day) in 13 healthy volunteers during steady state conditions.

Results: The therapeutically relevant parameter of 5-ASA at the rectal level, expressed as the mean concentration in faecal water, showed a significant trend towards higher concentrations with increasing Pentasa dose: 9.2 mmol/L, 19.0 mmol/L and 24.4 mmol/L, respectively. The concentration of olsalazine 2 g/day was 16.0 mmol/L. The concentration of the metabolite N-acetyl-5-aminosalicylic acid (Ac-5-ASA) did not rise with increasing Pentasa dose, indicating saturable presystemic acetylating capacity of 5-ASA. Total urinary excretion of 5-ASA and Ac-5-ASA, as a percentage of the daily ingested 5-ASA dose, remained constant on the three Pentasa doses, but there was a significant increase in the 5-ASA fraction. Mean steady state plasma concentrations of 5-ASA and Ac-5-ASA were significantly higher on Pentasa 4 g/day and 6 g/day than on 2 g/day. Values on Pentasa 2 g/day were comparable with those on olsalazine 2 g/day.

Conclusions: The study confirmed that 5-ASA is released from Pentasa in a predictable manner, the amount released increasing with dose. Olsalazine is an excellent generator of 5-ASA in the colon.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Oral
  • Aminosalicylic Acids / administration & dosage
  • Aminosalicylic Acids / analysis
  • Aminosalicylic Acids / pharmacokinetics*
  • Biological Availability
  • Delayed-Action Preparations
  • Drug Administration Schedule
  • Feces / chemistry
  • Humans
  • Mesalamine


  • Aminosalicylic Acids
  • Delayed-Action Preparations
  • Mesalamine
  • olsalazine