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.