Prodrug of Mesalazine: Medication compounded by union of two molecules of 5-ASA resulting in a dimer which is degraded into monomeric Mesalazine (5-ASA) in the large intestine. Mesalazine is badly absorbed by the intestine, serum levels are low with scant excretion into breast milk. Traces of Olsalazine and/or Mesalazine have not been found in breast milk of treated mothers with Olsalazine. N-acetyl-5-ASA is an inactive metabolite which is excreted into breast milk but not higher than 1% of relative infant's dose. No harm effects among breastfed infants from treated mothers have been reported, except for rare cases of diarrhea reported in the 80's with the use of Mesalazine compounds different to Olsalazine. In a review of 121 cases and 121 controls, the authors failed to observe those findings. (Moretti, 1989). Expert consensus supports the compatibility of Mesalazine and/or its prodrugs during breastfeeding.