Clinicians
at the AHT have recently completed a study into the efficacy
of Gabapentin as an adjunctive therapy for the management of
refractory epilepsy in dogs. Gabapentin has been used as an add
therapy in human epileptics refractory to the combination of
phenobarbitone and potassium bromide (KBr). It has an elimination
half-life of approximately 3-4 hours in dogs, and although should
ideally be administered every 6 hours, efficacy has been demonstrated
with three times daily dosing. Contrary to the situation in humans,
gabapentin is metabolised by the liver in dogs which puts this
species at risk of hepatotoxicity especially when gabapentin
is administered with phenobarbitone; however, this has not yet
been documented. In a study of 11 dogs, 45% demonstrated improved
seizure control with success based upon a 50% reduction in seizure
frequency.
The study included 11 dogs with refractory idiopathic epilepsy showing generalised
tonic-clonic seizures. Underlying causes were investigated using CSF tap and
MRI examination of the brain.
All
of the dogs were receiving a combination of phenobarbitone
and KBr and had therapeutic serum concentrations of these drugs.
Each dog received oral gabapentin for a minimum of three months
at an initial dose of 10 mg/kg q 8 hours.
Five
dogs showed a significant reduction in seizure frequency (ie
seizures reduced to less than 50% per week). However, many
dogs still exhibited multiple days on which there was cluster
seizure activity.
Gabapentin
was well tolerated - five dogs exhibited mild side effects
(ataxia and sedation). One dog developed sterile panniculitis
after 18 months but this resolved following cessation of gabapentin
treatment.
This
small study indicates that gabapentin may reduce seizure frequency
in some dogs with refractory idiopathic epilepsy. A larger
study is warranted to further evaluate the potential benefits
of gabapentin in epileptic dogs.
References
Platt
SR, Adams V, Garosi LS, et al (2003) Gabapentin as
adjunctive therapy
for refractory idiopathic epilepsy in dogs. Proc ECVN Annual Symposium
[abstract]
Radulovic
LL, Turck D, von Hodenberg A, et al (1995) Disposition
of gabapentin (neurontin)
in mice, rats, dogs, and monkeys. Drug Metab Disposition 23,
441-448. - PubMed -
Vollmer
KO, von Hodenberg A, Kolle EU (1986) Pharmacokinetics
and metabolism
of gabapentin in rat, dog and man. Drug Res 36, 830-839. - PubMed -
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