Immediate rhinoconjunctivitis induced by metamizole and metronidazole

Area of Science:

• Allergy and Immunology
• Pharmacology
• Otorhinolaryngology

Background:

• Immediate hypersensitivity reactions to medications can manifest in various ways.
• Rhinoconjunctivitis, characterized by nasal and ocular inflammation, is a less common presentation of drug allergy.
• Metamizole and metronidazole are distinct pharmaceutical agents with different therapeutic uses and known side effect profiles.

Observation:

• A patient presented with immediate rhinoconjunctivitis symptoms upon exposure to metamizole and metronidazole.
• Standard allergy testing, including skin prick tests, intradermal tests, and specific IgE (RAST) tests, were negative for both drugs.
• The patient tolerated other medications, including espyramicine, aspirin, and propyfenazone, without adverse effects.

Findings:

• Oral challenge tests with metamizole and metronidazole, as well as Rhodogil (a combination product containing metronidazole), reproduced the immediate rhinoconjunctivitis.
• The absence of positive skin tests and specific IgE antibodies suggests a non-IgE mediated hypersensitivity mechanism.
• Exclusion of cyclooxygenase pathway inhibition further complicates the understanding of the reaction's pathogenesis.

Implications:

• This case highlights an unusual presentation of immediate drug hypersensitivity.
• The underlying mechanism for this reaction to two unrelated drugs remains elusive, suggesting potential idiosyncratic or other immunologic pathways.
• Further research is needed to elucidate the mechanisms of non-IgE mediated drug hypersensitivity reactions.