What is the role of ondansetron (Zofran) in the management of paralytic ileus?

Ondansetron is Not Recommended for Paralytic Ileus

Ondansetron should not be used in the management of paralytic ileus as it may mask progressive ileus and gastric distention, and does not stimulate gastrointestinal peristalsis. 1

Mechanism of Action and Concerns

• Ondansetron is a serotonin 5-HT3 receptor antagonist primarily used for treatment of nausea and vomiting in various settings, not for stimulating bowel motility 2
• The FDA drug label specifically warns that ondansetron "may mask a progressive ileus and gastric distention" in patients following abdominal surgery 1
• Ondansetron is not a drug that stimulates gastric or intestinal peristalsis and should not be used instead of nasogastric suction 1

Pathophysiology of Paralytic Ileus

• Paralytic ileus is characterized by cessation of bowel motility without mechanical obstruction, leading to abdominal distention, pain, and potentially serious complications 3
• If left untreated, paralytic ileus can lead to severe complications including bowel perforation, ischemia, or death 4
• The condition is often associated with postoperative states, electrolyte imbalances, and medication effects (particularly opioids) 3, 4

Recommended Management Approach for Paralytic Ileus

First-line Management:

• Isotonic intravenous fluids should be administered when there is ileus (strong recommendation, moderate evidence) 2
• Correct any underlying electrolyte abnormalities that may contribute to decreased bowel motility 4
• Minimize or avoid opioid medications which can worsen ileus 3
• Early patient mobilization to help stimulate bowel function 3

Pharmacologic Interventions:

• Prokinetic agents may be considered to stimulate bowel motility, though evidence for their efficacy is limited 4
• In specific cases of Ogilvie's syndrome (acute colonic pseudo-obstruction), neostigmine administration has shown efficacy 5
• Some evidence suggests intravenous lidocaine infusion may shorten the duration of postoperative paralytic ileus by suppressing inhibitory gastrointestinal reflexes 6
• In rare cases of chemotherapy-induced paralytic ileus (e.g., vincristine), prostaglandin F2 alpha has been reported as potentially beneficial 7

Potential Adverse Effects of Ondansetron

• Using ondansetron in paralytic ileus may mask the progression of the condition, potentially delaying appropriate intervention 1
• Ondansetron carries risks including QT prolongation, hypersensitivity reactions, and serotonin syndrome 1
• The drug does not address the underlying pathophysiology of paralytic ileus and may complicate clinical assessment 1

Clinical Pitfalls to Avoid

• Do not confuse symptomatic management of nausea/vomiting with treatment of the underlying paralytic ileus 1, 4
• Avoid medications with anticholinergic properties as they may worsen ileus 2
• Early recognition and treatment of paralytic ileus is essential to prevent serious complications; masking symptoms with ondansetron may delay appropriate intervention 1, 4
• Remember that ondansetron is appropriate for facilitating oral rehydration in acute gastroenteritis with vomiting (particularly in children >4 years and adolescents), but this indication is distinct from paralytic ileus 2