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Chronic seizure disorders are classified as...
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Extracranial, Underlying causes for seizures (10):
- Hypocalcemia
- Hypoglycemia
- Hypoxia
- Hypo/Hypernatremia
- Hyper-triglyceremia
- Hepatic Encephalopathy
- Uremic Encephalopathy
- Polycythemia
- Thiamin Def
- Toxins
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Symptomatic, Intracranial, Underlying causes for seizures (9):
- Head Trauma
- Meningoencephalitis
- Hydrocephalus (other congenital)
- Cerebral Neoplasia
- Lysosomal Storage Disorder
- Acquired Cryptogenic Epilepsy
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Which type of seizure is most common in dogs?
Generalized tonic-clonic (Grand-Mal)
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Status Epilepticus-
When P fails to recover btw repeated tonic-clonic seizures, lasting for >30 mins
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Primary goals to inhibit seizures (3):
- Increase seizure threshold
- Reduce the spread of seizure discharge to surrounding neurons
- Reduce Discharge of Focus (less common)
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Drug therapy efficacy... Complete Control: Partial Control: Little/No Control:
- Complete: 50%
- Partial: 25%
- Little/None: 25%
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Drugs commonly used for status epilepticus:
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Drugs traditionally used for long term control of seizures:
- Phenobarb
- KBr
- (Primidone-hepatotoxic, Valpronic and Phenytion are limited in vet med)
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New drugs for long term control of seizures (5):
- Felbamate
- Gabapentine (neurontin)
- Levetiracetan (Keppra)
- Zonisamide (Zonegran)
- Pregabalin (Lyrica)
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Which Anticonvulsant is metabolized in the liver?
Phenobarb
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Which Anticonvulsant has active metabolites?
Diazapam
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What are the active metabolites of Diazapam?
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1/2 Life of... (Dogs/Cats)
Phenobarb:
Bromide:
Diazapam:
- Phenobarb: 2-3d/1-3d
- Bromide: 15-45d/10-11d
- Diazapam: 3hrs/15-20hrs
- (Dogs/Cats)
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Which Anticonvulsant is reabsorbed and excreted unchanged in the kidney?
Bromide
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Side Fx of Diazapam (4):
- Desation
- Ataxia
- Polyphagia
- ACUTE HEPATIC NECROSIS
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Side Fx of Bromide(5):
- Vomiting
- Sedation
- Polyphagia
- PU/PD
- Pelvic Limb Ataxia/Weakness
- (Rare: Hyperactivity, pancreatitis, cutaneous lesions, Inflammatory Lung Dz)
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Tx Strategy for dogs
- 1. Phenobarb
- 2. Pehnobarb + KBr
- 3. KBr alone
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Side Fx of Penobarb(7):
- Sedation
- Polyphagia
- PU/PD
- Pelvic Limb Ataxia/Weakness
- Hepatotoxic (+ALT & ALKP)
- Alter Bone Metab (Hematologic Fx)
- Increased metab of various subs (+T4/FT4, Abx)
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Tx strategy for cats
- 1. Phenobarb
- 2. Benzodiazapine
- 3. 3rd level drugs (primidone is toxic, and KBr=bronchial irritation)
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By which mechanisms does phenobarb supress seizures?
- Increase threshold
- Decrease Spread
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How does phenobarb work?
- GABA mediated inhibition
- Inhibits glutamate activity
- Reduces Ca fluxes across mem
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How does Diazapam work?
GABA Mediated Inhibition
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What drung enhances the action of GABA?
Benzodiazapine
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If Status Epilepticus doesn't respond to 2-3 doses of Diazapam, then admin...
Phenobarb IV
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Drawbacks of using Propofol to Tx Seizures (2):
- Hypotension
- Respiratory Depression
- (Expensive)
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In case of strychnine, ____ induces Status Epilepticus
Pentobarbital
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How long until Steady State obtained with administration of....
Phenobarb:
Br:
- Phenobarb: 10-16 days
- Bromide: 3-4 Months
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T1/2 of...
Phenobarb:
Br:
Diazapam:
- Phenobarb: 47-74/25-76 hrs
- Br: 15-45/10-11DAYS
- Diazapam: 3.2/15-20 hrs
- (Dogs/Cats)
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Which Anticonvulsants are contraindicated w/ Liver Dz?
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Which Anticonvulsants are contraindicated w/ Lung Dz?
Bromide
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Metabolism of Phenobarb
Liver
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Metabolism of Bromide
Unchanged in kidneys (reabsorbed= long 1/2 life)
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Metabolism of Diazapam
- 1st Passage
- Active Metabolites (Nordiazapam & Oxazapam)
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Diazapam's Active Metabolites
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Which anticonvulsants have an additive effect?
Bromide and Phenobarb
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Other/New Anticonvulsants (5):
- Febamate
- Gabapentine
- Levitiracetam
- Zonisamide
- Pregabalin
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Alt to Benzodiazapam for cats
Clonazepam
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Ways to protect brain function (5):
- Barbituates
- O2 therapy
- Mannitol
- Lasix
- Elevate head 30o
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Ways to support systemic function (5):
- Fluids
- O2Maint. Temp
- Maint HR & BP
- Ventilation (rarely)
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Most commonly used anticonvulsant
Phenobarb
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Congener of Phenobarb:
Primidone
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Primidone is converted to...
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Most potent elevator of threshold
Benzodiazapam
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By which mechanisms do effective anti-convulsives suppress seizures?
- Increase Threshol
- Inhibit Spread
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Which drugs is ineffective in dogs when given PO?
Diazapam
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Which drug requires a loading dose?
KBr/NaBr
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During sever convulsions (i.e. strychnine toxicosis) when diazapam is ineffective, what other drugs should be administered?
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