Suspected phenobarbital‐induced anticonvulsant hypersensitivity syndrome in a cat

Abstract

A six-month-old, uncastrated, male American shorthair cat was diagnosed with most likely primary epilepsy by history, laboratory examination and MRI. After 10 days of treatment with phenobarbital and levetiracetam, the cat developed inappetence and generalised lymphadenopathy. Cytological examination of the mandibular lymph nodes revealed hyperplastic and reactive lymph nodes. Based on patient history, clinical signs and laboratory test results, the signs may have been caused by antiepileptic drugs instead of lymphoma. Within seven days after cessation of phenobarbital, the cat’s mentation and skin oedema improved, and the lymph nodes were back to normal size. This is the first report of anticonvulsant hypersensitivity syndrome caused by phenobarbital in a cat in China.

Idiosyncratic reaction of topiramate in a Maine Coon cat

“…13 In previous reports of phenobarbital-associated AHS, adverse reaction was seen most commonly in 3-4 weeks after starting the phenobarbital and had rapid recovery once discontinued the drug. [3][4][5]14,15 In this cat, the AHS was noted at the similar time point in previous reports and no hematologic adverse reaction was recorded until topiramate was introduced. At the time neutropenia was discovered, the cat had already improved from the phenobarbital-associated AHS.…”

“…Once discontinued, the serum concentration decreased rapidly in 4 days 13 . In previous reports of phenobarbital‐associated AHS, adverse reaction was seen most commonly in 3–4 weeks after starting the phenobarbital and had rapid recovery once discontinued the drug 3–5,14,15 . In this cat, the AHS was noted at the similar time point in previous reports and no hematologic adverse reaction was recorded until topiramate was introduced.…”