Eperisone-induced immediate hypersensitivity reactions

Eperisone hydrochloride is a centrally acting muscle relaxant commonly prescribed for musculoskeletal pain, particularly in Korea and Japan. It induces relaxation of skeletal and vascular smooth muscle through central nervous system modulation and peripheral mechanisms, although its precise biochemical pathway remains unclear. While generally well tolerated, eperisone has been reported to cause immediate hypersensitivity reactions, including anaphylaxis. Because eperisone is frequently co-prescribed with non-steroidal anti-inflammatory drugs (NSAIDs), these reactions are often misdiagnosed as NSAID hypersensitivity, leading to unnecessary drug discontinuation and suboptimal pain management. A review of published case reports and pharmacovigilance data indicates that most eperisone-associated reactions are immediate-type, with anaphylaxis being clinically significant yet underrecognized. Skin prick tests and intradermal tests show variable diagnostic reliability, whereas drug provocation tests (DPTs) demonstrate the highest diagnostic accuracy and remain the gold standard. Basophil activation tests and serum tryptase measurement during DPT may serve as complementary diagnostic tools. Accurate identification of eperisone hypersensitivity is essential for preventing recurrent anaphylaxis and avoiding unnecessary NSAID discontinuation. This review summarizes the epidemiology, clinical features, and diagnostic strategies of eperisone hypersensitivity and emphasizes the importance of enhancing clinical awareness and referring affected patients to allergy specialists for proper evaluation.