D3.21 - When the Patient Diagnoses Herself: Amoxicillin-Induced Acute Pancreatitis as a Rare Manifestation of Drug Hypersensitivity

Introduction: Drug-induced pancreatitis (DIP) is a rare entity, constituting less than 2% of all acute pancreatitis cases. Although amoxicillin-clavulanate is widely prescribed, it is an uncommon cause of DIP. Diagnosis can be challenging, often relying on exclusion of more common etiologies. We report a case of Amoxicillin Clavulanate-induced pancreatitis in which the diagnosis was ultimately made after the patient herself suspected a drug reaction and pursued immunological assessment.

Case: A 45-year –old female presented to the Gastroenterology department with severe epigastric pain and nausea radiating to the back. Laboratory tests showed that amylase and lipase levels exceeded the upper standard limit by more than 3-fold. Abdominal CT confirmed acute edematous pancreatitis. Comprehensive workup excluded gallstones, biliary sludge (via ultrasound), hypercalcemia, hypertriglyceridemia, alcohol use, trauma, and recent ERCP. Viral and autoimmune markers (including IgG4) were negative. The etiology was initially deemed 'idiopathic.' However, the patient observed that her symptoms began 9 days after starting Amoxicillin Clavulanate for a dental infection and persisted post-discontinuation. Suspecting a link, she self-referred to the Allergy and Immunology department. The temporal association between drug initiation and symptom onset, with rigorous exclusion of other causes, provided Class Ib evidence for DIP. The Naranjo Adverse Drug Reaction Probability Scale indicated a "probable" relationship. She was advised to avoid Penicillins, and her symptoms entirely resolved without recurrence at follow-up.

Discussion: The mechanism of Amoxicillin Clavulanate-induced pancreatitis remains unclear but is believed to involve an idiosyncratic hypersensitivity reaction. The latency period for DIP can span from days to months, complicating timely recognition. In this case, the absence of typical allergic features such as rash or eosinophilia made the drug etiology less obvious. The diagnosis was based on the exclusion of other causes and the application of the Naranjo algorithm. Notably, this case highlights the crucial role of patient vigilance and self-advocacy in identifying rare adverse drug reactions when standard clinical markers are absent.

Conclusion: Drug-induced pancreatitis should be considered in patients with "idiopathic" pancreatitis, especially following recent antibiotic exposure. This case underscores the importance of careful patient history and the need to heed patients' suspicions, as rare drug reactions may present with isolated organ involvement in the absence of classic allergic signs.