Oral 5-HT3 receptor antagonist for at-home management of acute FPIES episodes in adults: A real-world observational study

Background Food protein–induced enterocolitis syndrome (FPIES) is increasingly recognized in adults. Because adults encounter diverse food environments, ingestion of trigger foods may occur despite dietary avoidance. However, the real-world occurrence of post-diagnosis FPIES episodes and strategies for at-home management remain poorly described. We aimed to characterize post-diagnosis FPIES episodes in adults and evaluate the real-world use of orally administered granisetron as a patient-initiated rescue treatment. Methods We conducted a retrospective observational study of adults diagnosed with FPIES between April 2023 and March 2025. Post-diagnosis FPIES episodes were recorded using patient diaries and a secure web-based reporting system. Patients were instructed to take granisetron (1 mg) when gastrointestinal symptoms developed after ingestion of a known trigger food. The primary outcome was time from granisetron intake to patient-reported symptom resolution. Time-to-event analyses were performed using Kaplan–Meier methods. Results Thirty-three FPIES episodes in 12 adults were treated with granisetron. Abdominal distention (84.8%), abdominal pain (75.8%), nausea (63.6%), and diarrhea (39.4%) were the most common symptoms. The median interval from symptom onset to granisetron intake was 30 min, and the median time from intake to symptom resolution was 50 min. Kaplan–Meier analysis showed symptom resolution rates of 45.5% at 30 min, 81.8% at 60 min, and 87.9% at 90 min. No emergency transport or intravenous treatment was required, and only mild constipation occurred in 2 episodes. Conclusion Oral granisetron may be associated with rapid symptom improvement and represent a potential patient-initiated option for at-home management of acute FPIES episodes in adults.