A Case of Codeine Induced Anaphylaxis via Oral Route.

Codeine is widely prescribed in clinical settings for the relief of pain and non-productive coughs. Common adverse drug reactions to codeine include constipation, euphoria, nausea, and drowsiness. However, there have been few reports of serious adverse reactions after codeine ingestion in adults. Here, we present a case of severe anaphylaxis after oral ingestion of a therapeutic dose of codeine. A 30-year-old Korean woman complained of the sudden onset of dyspnea, urticaria, chest tightness, and dizziness 10 minutes after taking a 10-mg dose of codeine to treat a chronic cough following a viral infection. She had previously experienced episodes of asthma exacerbation following upper respiratory infections, and had non-atopic rhinitis and a food allergy to seafood. A skin prick test showed a positive response to 1-10 mg/mL of codeine extract, with a mean wheal size of 3.5 mm, while negative results were obtained in 3 healthy adult controls. A basophil histamine release test showed a notable dose-dependent increase in histamine following serial incubations with codeine phosphate, while there were minimal changes in the healthy controls. Following a CYP2D6 genotype analysis, the patient was found to have the CYP2D6*1/*10 allele, indicating she was an intermediate metabolizer. An open label oral challenge test was positive. To the best of our knowledge, this is the first report of a patient presenting with severe anaphylaxis after the ingestion of a therapeutic dose of codeine, which may be mediated by the direct release of histamine by basophils following exposure to codeine.