Anticonvulsants In Small Animals Flashcards
(23 cards)
Primary mechanism of benzodiazepines
Activate Gaba-gated Cl- channels enhancing GABA inhibitory effects — cause neuronal hyperpolarization
Why are benzodiazepines preferred for status epilepticus
Rapid onset (IV) and potent suppression of seizure activity
Which benzodiazepines is used for long term in cats but not in dogs and why?
Diazepam (oral)
Dogs develop rapid tolerance
Cats have longer half life and lower tolerance risk
What are the routes of administration for diazepam ?
IV(emergency)
Oral(cats)
Intrarectal(dogs-well tolerated)
Avoid IM -slow absorption due to propylene glycol
Name 2 active metabolites of diazepam
Nordiazepam(desmethyldiazepam)
Temazepam
What is a severe adverse effect of oral diazepam in cats?
Acute fatal hepatic necrosis
How does midazolam solubility change with pH?
Water soluble at ph <4 (bottle)
Lipid soluble at pH (7.4) rapidly crosses BBB
Compare midazolams duration to diazepam
Shorter half life =77 minutes in dogs vs diazepams =2-4 hours
What is phenobarbital mechanism of action?
Enhances GABA-gated Cl- channels — elevates seizures threshold
Why is phenobarbital unsuitable for acute seizures?
Slow onset (20 minutes ) used for long term control
Name common side effects of phenobarbital
Sedation
3Ps -polydipsia, Polyuria , polyphagia
Hepatotoxicity
What is phenobarbital half life
32-90hrs long - requires 14 days to reach steady state
Why is Potassium Bromide used in refractory seizures?
No metabolism/ protein binding , long half life (25 days in dogs)
Why is kBr contraindicated in cats
Causes severe asthma
How is KBr eliminated
Exclusively renal ( no liver metabolism)
What is primary mechanism of gabapentin
Inhibits voltage gated Ca+2 channels to reduce glutamate release
Name a key adverse effect if gabapentin is abruptly discontinued
Seizures (must taper dose)
What is unique mechanism of Levetiracetam ?
Bind to synaptic vesicles protein 2A (SV2A) to reduce seizure propagation
Why is levetiracetam well tolerated in dogs and cats?
Minimal side effects ie ( GI upset,mild drowsiness)
Why is valproic cause rarely used long term in dogs?
Short half life and hepatotoxicity risk
Name 2 hematologic adverse effects of valproic acid
Thrombocytopenia
Leukopenia
Which drug treats digitalis-induced arrthythmias due to lidocaine like effects ?
Phenytoin but rarely used for seizures due to short half life in dogs
Which drugs metabolite contributes to 85% of its anticonvulsant activity
Primidone converted to phenobarbital
