Drug Levels and Effects:

Summary of Use during Lactation:

Limited data indicate that olsalazine is poorly excreted into breastmilk. However, olsalazine is a mesalamine prodrug. Rather high levels of the mesalamine metabolite N-acetyl-5-ASA appear in breastmilk and its effects on breastfed infants are unknown. A few cases of diarrhea have been reported in infants exposed to mesalamine, although the rate is not high. European experts consider mesalamine derivatives to be safe during breastfeeding.[1] If olsalazine is required by the mother, it is not a reason to discontinue breastfeeding, but carefully observe breastfed infants for diarrhea during maternal use of olsalazine.

Drug Levels:

Olsalazine is a prodrug that liberates the active drug, mesalamine (5-aminosalicylic acid; 5-ASA), in the gastrointestinal tract. Mesalamine is metabolized to N-acetyl-5-ASA which is inactive in treating inflammatory bowel disease, but its possible effects on the breastfed infant are unknown.

Maternal Levels.

A lactating woman with a long history of Crohn's disease and 2 bowel resections at her terminal ileum was given a single oral dose of olsalazine 500 mg at 4 months postpartum. She was also taking prednisone 17.5 mg daily at the time of the study. Milk samples were taken periodically from 30 minutes to 48 hours after the dose. Olsalazine and its metabolites, olsalazine sulfate and mesalamine were undetectable (<170 mcg/L) in milk at all times during the study. The inactive mesalamine metabolite, N-acetyl-5-ASA, was detectable only at 10, 14 and 24 hours after the dose in concentrations of 170, 183 and 264 mcg/L, respectively.[2]

A woman taking olsalazine capsules 750 mg twice daily collected 5 breastmilk samples during one day 2 to 4 weeks postpartum. Mesalamine was undetectable (<20 mcg/L) in milk. N-acetyl-5-ASA averaged 2.3 mg/L (range 1.2 to 3.8 mg/L) in the 5 samples. The highest milk level was in the 6 pm sample, but the times of the doses were not stated.[3]

Infant Levels.

Relevant published information was not found as of the revision date.

Effects in Breastfed Infants:

One infant was breastfed during maternal therapy with olsalazine for Crohn's disease. After 2 and 3 weeks of therapy, no rash, wheezing, vomiting or diarrhea were noted in the infant.[2]

The active metabolite of olsalazine, mesalamine, was probably responsible for diarrhea in a 6-week-old whose diarrhea recurred 4 times after rechallenge of the mother 4 times during breastfeeding.[4]

Diarrhea has also been reported anecdotally by some nursing mothers,[5] but a small controlled study reported only in abstract form found no higher rate of diarrhea in the breastfed infants of mothers taking mesalamine than in control infants.[6]

Possible Effects on Lactation:

Relevant published information was not found as of the revision date.

Alternate Drugs to Consider:



1. van der Woude CJ, Kolacek S, Dotan I et al. European evidenced-based consensus on reproduction in inflammatory bowel disease. J Crohn's Colitis. 2010;4:493-510. PMID:21122553
2. Miller LG, Hopkinson JM, Motil KJ et al. Disposition of olsalazine and metabolites in breast milk. J Clin Pharmacol. 1993;33:703-6. PMID:8408729
3. Christensen LA, Rasmussen SN, Hansen SH et al. Salazosulfapyridine and metabolites in fetal and maternal body fluids with special reference to 5-aminosalicylic acid. Acta Obstet Gynecol Scand. 1987;66:433-5. PMID:2892343
4. Nelis GF. Diarrhoea due to 5-aminosalicylic acid in breast milk. Lancet. 1989;333:383. Letter. PMID:2563532
5. Ito S, Blajchman A, Stephenson M et al. Prospective follow-up of adverse reactions in breast-fed infants exposed to maternal medication. Am J Obstet Gynecol. 1993;168:1393-9. PMID:8498418
6. Moretti ME, Spiczynski Y, Hashemi G et al. Prospective follow-up of infants exposed to 5-aminosalicylic acid containing drugs through maternal milk. J Clin Pharmacol. 1998;38 (Suppl):867. Abstract.

Substance Identification:

Substance Name:


CAS Registry Number:


Drug Class:

  • Gastrointestinal Agents

  • Anti-Inflammatory Agents, Non-Steroidal

  • Administrative Information:

    LactMed Record Number:


    Last Revision Date:

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