Disposition of 5-aminosalicylic acid and N-acetyl-5-aminosalicylic acid in fetal and maternal body fluids during treatment with different 5-aminosalicylic acid preparations

Acta Obstet Gynecol Scand. 1994 May;73(5):399-402. doi: 10.3109/00016349409006251.


Study objective: To determine the concentration of 5-aminosalicylic acid (5-ASA) and the metabolite N-acetyl-5-aminosalicylic acid (Ac-5-ASA) in the maternal and fetal plasma at delivery and in the maternal milk post partum.

Design and study subjects: Pregnant and lactating women with chronic inflammatory bowel disease, treated with different pure 5-ASA preparations participated in the study. At delivery, samples of fetal and maternal plasma were obtained from nine women. The excretion in milk was measured and the time of medicine intake was registered during a 24 h period 2-4 weeks after delivery in 13 women.

Results: Concentrations of 5-ASA in the fetal plasma were lower than in maternal plasma. Plasma concentrations of Ac-5-ASA were detectable in all the nine samples and similar levels in the mother and the fetus were found at the time of delivery. In three women 5-ASA was detected in the milk in low concentrations. The concentration of Ac-5-ASA in the milk varied considerably during the 24 h collection period, and also between individuals; its concentration tended to be higher than in the plasma. No time relation between medicine intake and maximal concentration in the milk was found. Based on the maximal Ac-5-ASA concentration and a milk intake of one liter/daily, the newborn receives less than 15 mg Ac-5-ASA daily.

Conclusion: The study indicates that treatment with pure 5-ASA preparations in conventional doses is without risk to the fetus and the newborn.

MeSH terms

  • Aminosalicylic Acids / blood
  • Aminosalicylic Acids / pharmacokinetics*
  • Aminosalicylic Acids / supply & distribution
  • Aminosalicylic Acids / therapeutic use*
  • Drug Monitoring
  • Female
  • Fetal Blood / chemistry*
  • Fetus / drug effects*
  • Humans
  • Inflammatory Bowel Diseases / blood*
  • Inflammatory Bowel Diseases / drug therapy*
  • Mesalamine
  • Milk, Human / chemistry*
  • Pregnancy
  • Pregnancy Complications / blood*
  • Pregnancy Complications / drug therapy*
  • Time Factors
  • Tissue Distribution


  • Aminosalicylic Acids
  • Mesalamine
  • N-acetyl-5-aminosalicylic acid