The active metabolite of olsalazine, 5-aminosalicylic acid (mesalamine), is excreted into human milk (see Mesalamine). In one study, however, only a metabolite of mesalamine, acetyl-5-aminosalicylic acid, was detected in breast milk after the ingestion of olsalazine (see Mesalamine) (4). Because diarrhea has occurred in a nursing infant of a mother receiving mesalamine (see Mesalamine), nursing infants of women being treated with olsalazine should be closely observed for changes in stool consistency. The most common adverse reactions observed in adults are diarrhea/loose stools, abdominal pain, and rash/itching (1). If a woman is receiving this drug while breastfeeding, her nursing infant should be monitored for these effects.

Olsalazine is indicated for the maintenance of remission of ulcerative colitis in patients who are intolerant of sulfasalazine. It is poorly absorbed, approximately 2.4% after oral administration, with the remainder reaching the colon intact where it is converted into two molecules of 5-aminosalicylic acid (mesalamine) by colonic bacteria. About 0.1% of an oral dose is metabolized in the liver. Plasma protein binding is >99%, and the serum half-life is about 0.9 hour (1). The history, pharmacology, and pharmacokinetics of mesalamine and olsalazine were extensively reviewed in a 1992 reference (2).

Animal Data: Reproductive studies with olsalazine in rats have revealed reduced fetal weights, retarded ossifications, and immaturity of the fetal visceral organs with doses 5-20 times the recommended human dose on a weight basis (1).

Olsalazine was carcinogenic in male rats and mice. Multiple assays for mutagenesis were negative, and no effects on fertility were noted in male and female rats (1).

Placental Transfer: It is not known if olsalazine crosses the human placenta. The molecular weight (about 346) is low enough, but the small amounts absorbed systemically and the very short serum half-life suggest that clinically significant exposure of the embryo and/or fetus is unlikely.

Human Data: A 2008 meta-analysis studied the risk of adverse pregnancy outcomes in women with inflammatory bowel disease (IBD) following exposure to 5-aminosalicylic acid drugs (olsalazine, balsalazide, mesalazine, and sulfasalazine) (3). In 7 studies, 1158 received no medication and 642 received 5-aminosalicylic acid drugs. There was no statistically significant increase in birth defects, stillbirths, spontaneous abortion, preterm delivery, and low birth weight (3).