Anticonvulsants Flashcards
Epilepsy
spontaneous episodes associated w/ loss or disturbances of consciousness, usually but not always accompanied by characteristic body movements and always excessive EEG discharge
Seizure
transient alteration of behavior due to disordered, synchronous and rhythmic firing of a population of brain neurons
Focal or partial seizure
60% of epilepsies, originates in one hemisphere of brain, usually due to lesion: head trauma, tumor, stroke, hypoxia at birth, metabolic disorders, malformations, can progress to generalized seizures
Generalized seizures
originates from both hemispheres simultaneously, loss of consciousness
Status epilepticus
failure of seizure termination>5 mins
Tonic-clonic
loss of consciousness w/ tonic stiffening followed by clonic muscle activity
isolated tonic
mostly in children, increased tone in extensors
isolated clonic
mostly in small children and babies
Atonic
abrupt loss of all muscle tone; patients fall
Absence
hardest to treat, commonly seen in children, brief loss of awareness and behavioral arrest, inhibition of GABA receptors, activation of T-type Ca current leading to hypperpolerization
Myoclonic
sudden or split second, contraction of a muscle or group of muscles
Lennox Gastaut syndrome
difficult to control seizure disorder where pt usually has myoclonic, atonic, absence and tonic seizures
Pathophysiology of seizures
not well understood, imbalance between excitatory and inhibitory neurons
Non-pharm treatment
surgery, ketogenic diet, vagal nerve stimulator
Goals of AEDs
decrease seizures, minimize adverse effects of seizures
AEDs MOA
inhibit Na channels, inhibit Ca channels, potentiate K channels, increase GABA, decrease glutamate
Barbiturates
Phenobarbital, primidone (Mysoline), Prntobarbital (Nembutol), Methohexital (Brevitol)
Barbiturates MOA
binds to allosteric modulation site that is present at a/B subunits of GABA, coupled to Cl channels they open in presence of GABA permitting influx of Cl and hyperpolerizes cell, barbiturates cause cl channel to stay open
Phenobarbitol
effective in tonic-clonic, and focal seizures, DOC for neonatal seizures, IV/PO, cheap, can be monitored
ADRs of phenobarbitol
sedation, depression of mood, cognitive impairment, hepatoxicity, lots of DIs
Primidone (Mysoline)
major metabolite of phenobarbitol, DOC for essential tremor, second line for focal and tonic clonic, very sedating, sometimes status epilepticus, primary use for pentobarbital coma
Phenytoin (Dilantin) MOA
Na channel blocker that binds the inactive channel and inc the time it takes to recover to the active state, prolonged recovery time limits high-freq firing, some use in antiarrythmias
Phenytoin (Dilantin) indications
focal w/and w/out 2nd generalization, sometimes primary generalized tonic clonic, eizure prevention following neurosurgery, not effective for atonic, absence or myoclonic seizures
Phenytoin (Dilantin)
IV/PO must drug monitor, narrow therapeutic index, nonlinear kinetics, status: load w/ 15-20 mg/kg IV/PO, maintenance 100 mg PO TID to start, normal levels 10-10 mcg/ml, adjust for protein, many DI
Phenytoin ADRs
sedation, nausea, nystagmus, dizziness, cog impair, ataxia, SJS, hepatic toxicity aplastic anemia, gingival hyperplasia, hirsutism, folate defiency and osteopenia
Fosphenytoin (Cerebyx)
IV prodrug of phenytoin, less ADRs, infused faster 150 mg/min, loading does 100 mg IV, IV/IM
Benzodiazepines
Diazepam (Valium), Lorazepam (Ativan), Midazolam (Versed), Clonazepam (Klonipin), Clobazam (Onfi)
Benzo MOA
bind to allosteric modulation site of GABA receptor, GABA linked to Cl channel, when GABA and Benzos are bound to receptors they follow more frequent opening of channels, and thus more hyperpolarization