muscle contractions and periods of cyanosis May be proceeded by a loud cry caused by forceful expiration of air across the vocal cords o Characterized by a period of muscle rigidity Followed by synchronous muscle jerk o Often cause urination but not defecation o Accompanied by marked impairment of consciousness and CNS depression (postictal state) o Lasts 90 secs or less Absence seizures o Characterized by loss of consciousness for brief time o Mild symmetric activity (eye blinking) no motor activity Atonic seizures o Sudden loss of muscle tone Head drop(neck Drop attack (limbs and trunk) o Mainly in children Myoclonic o Sudden muscle contraction that lasts 1 second One limb—focal myoclonus Entire body—massive myoclonus Status epilepticus o Persists for 15-30 min or longer o Patients does not regain consciousness o Types Generalized convulsive deadly Absence Myoclonic
Febrile o Fever associated; children 6m-5 yr o Manifest as generalized tonic-clonic convulsions of short duration o Not high risk for epilepsy later in life Mixed Seizure: Lennoc-Gastaut Syndrome Severe Dev in preschool years Characterized by developmental delay and mixture of partial and generalized seizures o Difficult to manage Seizures involves o Partial, o Atonic o Tonic o Generalized tonic-clonic o Atypical absence How antiepileptic drugs work Suppression of sodium influx Phenytoin, carbamazepine, and lamotrigine reversibly bind to sodium channels while they are in the inactivated state and prolong channel inactivation. By delaying return to active state, ability of neurons to fire @ high freq decreases o Result—seizures that depend on high freq discharge are suppressed Suppression of calcium influx In axon terminals, influx of calcium occurs thru voltage gated calcium channels and promotes transmitter release Drugs that block calcium channels can suppress transmission o Ethosuximide Promotion of Potassium Efflux Ezogabine acts on voltage gated potassium channels to facilitate potassium efflux o This underlies the drugs ability to slow repetitive neuronal firing and provide seizure control Antagonism of glutamate Works thru NMDA and AMPA receptors Perampanel is AMPA glutamate antagonist Felbamate and topiramate block actions of glutamate at NMDA receptors suppressing neuronal excitation Potentiation of GABA By augmenting inhibitory influence of GABA, neuronal excitability is decreased, and seizures are suppressed Benzos and barbiturates enhance GABA by mechanisms that involve direct binging to GABA
Gabapentin promoted GABA release Tiagabine inhibits GABA reuptake and vigabatrin inhibits the enzyme that degrades GABA which increases GABA availability Basic therapeutic considerations Therapeutic goal and treatment options Goal—reduce seizures so that pt. can live normal life May cause intolerable side effects o Balance adverse and therapeutic effects Diagnosis and drug selection Drugs selected for specific disorders Partial
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- Spring '14
- Adrenergic receptor, Phenytoin