TOPIC 15: ANTICONVULSANTS/ANTI-SEIZURE/ANTIEPILEPTIC

Phenobarbital

Barbiturate anticonvulsant

Mephobarbital

Barbiturate anticonvulsant, metabolized in the liver to phenobarbital

Pentobarbital

Barbiturate anticonvulsant, effective against refractory status epilepticus

Primidone

• Deoxybarbiturate anticonvulsant.

• Metabolized to phenobarbital and PEMA.

• Inhibits voltage-gated sodium channels.

Phenytoin

• Hydantoin anticonvulsant.

• Blocks voltage-gated sodium channels.

Mephenytoin

• Hydantoin anticonvulsant.

• Metabolized to active metabolite nirvanol

Fosphenytoin

Water-soluble prodrug of phenytoin, suitable for IV administration, effective against status epilepticus and persistent generalized seizure activity in dogs, causes less local irritation than injectable phenytoin

Diazepam

Benzodiazepine anticonvulsant, effective against active generalized convulsive seizures, status epilepticus, cluster seizures, and toxin-induced or reactive seizures

Clonazepam

Benzodiazepine anticonvulsant

Clorazepate

Benzodiazepine anticonvulsant prodrug, converted to nordiazepam

Valproic Acid

Blocks voltage-gated sodium channels, decreases GABA degradation, increases GABA synthesis and CNS GABA concentration, blocks T-type calcium channels, effective against focal seizures, generalized tonic-clonic seizures, myoclonic seizures, and absence seizures, may cause hepatotoxicity

Sodium Valproate

Blocks voltage-gated sodium channels, decreases GABA degradation, increases GABA synthesis and CNS GABA concentration, blocks T-type calcium channels, effective against focal seizures, generalized tonic-clonic seizures, myoclonic seizures, and absence seizures, may cause hepatotoxicity

Potassium Bromide

Competes with chloride ions, passes through GABA-gated chloride channels causing neuronal hyperpolarization, effective against focal-onset seizures, generalized tonic-clonic seizures, maintenance treatment of canine idiopathic epilepsy, and refractory seizures with phenobarbital, excreted unchanged by the kidneys, not hepatically metabolized

Sodium Bromide

Bromide anticonvulsant

Ethosuximide

Blocks T-type calcium channels, effective against absence seizures and distemper-associated myoclonus or reflex spasms in dogs, not effective against generalized tonic-clonic convulsions

Gabapentin

Binds alpha-2-delta-1 subunit of voltage-gated calcium channels, decreases calcium entry and glutamate release, effective against focal-onset seizures, focal seizures progressing to generalized seizures, and refractory epilepsy, more commonly used for neuropathic pain

Pregabalin

Similar to Gabapentin

Vigabatrin

Irreversibly inhibits GABA transaminase, decreases GABA breakdown, increases synaptic GABA and neuronal inhibition

Felbamate

Blocks NMDA receptors, inhibits voltage-gated sodium channels, enhances GABAA receptors, effective against complex focal seizures, focal seizures with secondary generalization, and refractory generalized seizures, mainly used as an adjunct for drug-resistant epilepsy

Zonisamide

Blocks sodium channels and calcium channels

Levetiracetam

Binds SV2A vesicle proteins, reduces excitatory neurotransmitter release, blocks hyper-synchronous neuronal firing, effective against focal-onset seizures, generalized tonic-clonic seizures, myoclonic seizures, cluster seizures, and status epilepticus as an emergency adjunct