New anticonvulsant drugs
Gabapentin appears to exert its anticonvulsant effect primarily via interaction with neuronal voltage-gated calcium channels.
Inhibition of these channels is thought to decrease excitatory neurotransmission. Gaba-
pentin typically is administered orally at a dosage of 10 mg/kg every eight hours in dogs. There are anecdotal reports of
gabapentin use in cats with seizures (5-10 mg/kg PO, q8-12 hours).
Clinical efficacy reports in refractory epileptic dogs treated with gabapentin as an add-on therapy indicate that fewer than
half of such dogs are responders (i.e., experience a 50 percent or more reduction in seizures after adding gabapentin). However,
gabapentin is the least effective of the new anticonvulsant drugs. Side effects typically are mild, and include minor sedation
and pelvic limb ataxia.
Gabapentin is available in generic form at a much lower price than the trade-name formulation.
Felbamate is suspected to exert its anticonvulsant effects via potentiating GABA-mediated neuronal inhibition, mitigating
NMDA-mediated neuronal excitation and inhibiting voltage-gated neuronal sodium and calcium channels.
Felbamate typically is dosed initially at 15 mg/kg orally every eight hours. There is limited published information regarding
its efficacy, but it is generally believed to be an effective anticonvulsant add-on agent. Side effects are uncommon, but
hepatotoxicity (usually with concurrent high phenobarbital blood levels), reversible blood dyscrasias and keratoconjunctivitis
sicca have been reported with felbamate use in dogs. There is no information on its use in cats.
Considering the hepatic and blood dyscrasia issues associated with felba-
mate use in humans and dogs (uncommon as they may be), it is unlikely that there will be much impetus to pursue research into
feline felbamate use. There is no generic formulation available for felbamate.