Hypersensitivity reaction associated with subcutaneous glargine insulin therapy in a cat.

CASE SUMMARY: A 14-year-old, domestic shorthair cat was treated for transient diabetes mellitus for 3 months with glargine insulin, which was discontinued when the diabetes mellitus resolved. Approximately 36 months later the diabetes mellitus recurred and glargine insulin was restarted. Within 2-3 mins of the first injection the cat collapsed, developed profuse vomiting and diarrhea, as well as facial swelling and diffuse erythema. A hypersensitivity reaction was suspected and the cat was treated with antihistamines, aggressive fluid therapy and gastrointestinal support. The cat made a full recovery and was discharged 3 days later. Six months later the cat re-presented for relapse of its diabetes mellitus and an intradermal skin challenge with 1:20 diluted insulin was performed confirming a hypersensitivity to glargine. The cat continues to be well regulated on porcine zinc insulin without any hypersensitivity reactions noted.

RELEVANCE AND NOVEL INFORMATION: Hypersensitivity reactions to insulin administration are rarely described in human medicine. This is the first reported case of a hypersensitivity reaction secondary to glargine insulin in a cat. Clinicians should be aware of this potential complication, particularly in animals with a previous history of insulin administration and the potential to utilize intradermal testing with insulin.