From the Guidelines
Yes, ondansetron can make constipation worse, as it slows down the movement of the intestines, leading to harder stools and less frequent bowel movements in some patients. This is supported by a study published in 2021 in the journal Gut, which found that ondansetron, a 5-HT3 receptor antagonist, can cause constipation as a side effect 1. The study noted that constipation is the most common side effect of ondansetron, and that it can be a significant issue for patients taking this medication.
To manage constipation while taking ondansetron, patients can try staying well-hydrated, increasing dietary fiber intake, and maintaining physical activity. For persistent constipation, patients can discuss with their healthcare provider about adding a gentle laxative such as polyethylene glycol (Miralax), docusate sodium (Colace), or senna. It's also important for patients to inform their prescriber about any history of constipation or bowel disorders, as they may recommend preventive measures or alternative anti-nausea medications with less impact on bowel function.
It's worth noting that the American Gastroenterological Association has guidelines for managing opioid-induced constipation, which may be relevant for patients taking ondansetron, although ondansetron is not an opioid 1. However, the guidelines do provide general advice on managing constipation, which may be applicable to patients taking ondansetron.
In terms of specific management strategies, the study published in Gut found that ondansetron can be effective in improving stool consistency in patients with irritable bowel syndrome with diarrhea, but it can also cause constipation as a side effect 1. Therefore, patients taking ondansetron should be monitored for constipation and managed accordingly.
Overall, the evidence suggests that ondansetron can make constipation worse, and patients taking this medication should be aware of this potential side effect and take steps to manage it.
From the FDA Drug Label
In addition to the adverse reactions listed above, the following adverse reactions have been described in the setting of ondansetron overdose: “Sudden blindness” (amaurosis) of 2 to 3 minutes’ duration plus severe constipation occurred in one patient that was administered 72 mg of ondansetron intravenously as a single dose Constipation is listed as an adverse reaction in the context of an ondansetron overdose.
- The FDA drug label does mention constipation as a potential adverse reaction, but only in the context of an overdose.
- There is no direct information in the label that suggests ondansetron makes constipation worse at recommended doses.
- However, it can be inferred that ondansetron may contribute to constipation, especially at high doses, as evidenced by the reported case of severe constipation in the setting of an overdose 2.
From the Research
Ondansetron and Constipation
- There is no direct evidence from the provided studies that ondansetron makes constipation worse 3, 4, 5, 6, 7.
- However, a study on the effect of ondansetron on irritable bowel syndrome with diarrhea domination found that ondansetron increased stool consistency and reduced the frequency of diarrhea 4.
- Other studies focused on the treatment of chronic constipation with over-the-counter therapies, recommending polyethylene glycol and senna as first-line laxatives, but did not mention ondansetron as a treatment for constipation 5, 6.
- A study comparing ondansetron, metoclopramide, and placebo for nausea and vomiting in adult emergency department patients did not report constipation as an adverse event 7.
Adverse Events
- Common adverse events reported in the studies included headache, sedation, abdominal pain, cramping, bloating, diarrhea, and nausea 3, 5, 6, 7.
- However, constipation was not mentioned as an adverse event in any of the studies 3, 4, 5, 6, 7.