Proceedings 31st Symposium ESVN-ECVN

Seventy‐seven cats, 58 with idiopathic epilepsy and 19 with structural epilepsy, met the inclusion criteria. One or more of the following adverse effects were reported in 47% (36/77) cats: sedation 89% (32/36), ataxia 53% (19/36), polyphagia 19% (7/36), polydipsia 6% (2/36), polyuria 6% (2/36) and anorexia 6% (2/36). Median phenobarbitone dosage at the time of adverse effect onset was 2 mg/kg (range 1.25‐5 mg/kg) BID. Adverse effects were known to resolve following achievement of steady state or following dose reduction in 20 cats. Logistic regression analyses revealed a significant association between phenobarbitone dose and occurrence of adverse effects. For each increment of 1 mg/kg BID, the risk of ataxia increased 2.9 times and the risk of sedation increased 3 times. Epilepsy aetiology and administration of a second antiepileptic drug were not associated with adverse effect occurrence. Idiosyncratic adverse effects, characterised by severe neutropenia and severe granulocytic hypoplasia, were diagnosed in only one cat. These resolved following phenobarbitone discontinuation.