Intestinal obstruction is a rare complication of ondansetron exposure in hyperemesis gravidarum.

This letter is in response toCohenet al., “Intestinal obstruction in pregnancy by ondansetron.” The article concludes that “the serious adverse effect of ondansetron is probablymuchmore common, and has been the subject of under reporting.” We have been collecting extensive survey data on women with severe nausea of pregnancy in an IRB approved study since 2007. Participants are asked to reportmedications/treatments, complications and side effects. The majority of participants fill out the survey while they are pregnant and are prompted to complete the survey after their due date, and provide follow-up biannually afterwards. Currently we have 877 women in our database reporting on 1193 pregnancies exposed to ondansetron. Among the 1193 ondansetron exposures, there have been 3 (0.25%) reports of hospitalization for intestinal obstruction. The first patient took ondansetron all 3 trimesters for 38 weeks every 6h, 24mg/day. The second patient took ondansetron for 3 weeks in the first trimester only, 16mg/day. The third patient took ondansetron all 3 trimesters for 35 weeks every 6h, 32mg/day. Delayed gastric emptying was reported in 107 (8.97%) of pregnancies exposed to ondansetron. Severe constipation was reported in 36 (3.02%) pregnancies. We conclude that intestinal obstruction in pregnancies exposed to ondansetron is rare, and that the antiemetic benefit outweighs the risk of intestinal obstruction for the majority of pregnant women with severe nausea and vomiting. However, caregivers and patients should be aware of the risk of intestinal obstruction. We strongly encourage proactive hydration management and implementation of a regular bowel regimenwith laxatives and stool softeners. If constipation becomes severe, we recommend lowering the dose of medication or switching to an alternative antiemetic therapy.