- blocks sustained high frequency firing of APs d/t preferential binding and prolongation of inactivated NaCh - decrease synaptic release of glutamate and enhances release of GABA

anticonvulsant drugs Flashcards by laura gibbons

epilepsy

occurrence of at least 2 unprovoked seizures separated by 24 hours

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partial/focal seizures

localized onset, ascertained either by observation or EEG
3 subcategories: 
-simple partial
-complex partial
-secondarily generalized seizure

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simple partial seizure

minimal spread of abnormal discharge
normal consciousness
perserved awareness

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complex partial seizure

localized onset, but discharge becomes widespread, almost always involves limbic system
pt may have automatisims, memory loss, aberrant behavior

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secondarily generalized seizure

partial seizure immediately precedes a generalized tonic-clonic seizure

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generalized seizures

those w/o evidence of localized onset
clinical manifestation indicate involvement of both brain hemispheres 
4 subcategories:
-generalized tonic-clonic/grand mal
-absence/ petit mal
-myoclonic jerking
-atonic

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generalized tonic-clonic/grand mal

sudden sharp tonic contraction followed by rigidity and clonic mvmts
pt may cry/moan, lose sphincter control, bite tongue, cyanotic
after seizure pt may have altered consciousness, drowsiness, or confusion

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absence/petit mal

sudden onset and abrupt cessation, altered consciousness, blank stare
young kids-adolescence

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myoclonic jerking

brief, shock-like mm contraction’

occur in wide variety of seizures

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atonic seizures

sudden loss of postural tone, head drop, fall to floor, slumping
many pts wear helmet

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generalization of Rx seizure Tx

suppress do not cure
should try different monotherapies before combining drugs
compliance is VERY important
generics may not be a good idea

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MOA of AEDs in general

affect ion Ch kinetics (delay NaCh recovery)
augmenting inhibitory neurotransmission
modulating excitatory neurotransmission

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PK of AEDs in general

cleared chiefly by hepatic metabolism

many are potent CYP inducers

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general ADRs of AEDs

common neurotoxic effects- sedation, dizziness, blurred or double vision, difficulty concentrating, and ataxia

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phenytoin MOA

blocks sustained high frequency firing of APs d/t preferential binding and prolongation of inactivated NaCh
decrease synaptic release of glutamate and enhances release of GABA

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phenytoin PK

cannot be given IM- fosphenytoin can be injected
highly protein bound 
elimination dose-dependent
CYP meta
narrow therapeutic index

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phenytoin uses

partial seizures

generalized tonic-clonic seizures

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phenytoin ADRs

gingival hyperplasia, hirsutism
in early use can present w/rash, fever, hepatits, and lymphadenopathy,
rarely causes dermatits and stevents-johnson syndrome

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phenytoin long term ADRs

worsening facial features
mild peripheral neuropathy
vit D meta abnormalities -> osteomalacia

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phenytoin cardiac ADRs

hypotension, bradycardia, cardiac arrythmia, CV collapse, venous irritation, pin, thrombophlebitis

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Phenytoin DDIs

related to protein binding- sulfonamides

related to meta- warfarin (increased INR), OBC (increased risk of prego)

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carbamazepine and oxcarbazepine MOA

NaCh -> inhibit high frequency repetitive firing

also acts presynaptically to decrease release of glutamate

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carbamazepine and oxcarbazepine PK

hepatic meta

potent CYP inducer (including its own meta)

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carbamazepine and oxcarbazepine uses

partial seizures, generalized tonic-clonic seizures, trigeminal neuralgia, mania in bipolar disorder

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carbamazepine and oxcarbazepine ADRs

``` hyponatremia and water intoxication blood dyscrasias (fatal aplastic anemia and agranulocytosis, leukopenia)- monitor mild rash to stevens-johnson syndrome ```

carbamazepine and oxcarbazepine DDIs

increases meta of primidone, phenytoin, OBC, valpronic acid | valpronic acid may decrease clearance

gabapentin and pregabalin MOA

analogs of GABA, but do not act directly on GABAR | bind N-type CaCh -> decrease Ca entry -> decrease release of glutamate

gabapentin uses

partial seizures generalized tonic-clonic seizures neuropathic pain post-herpetic neuralgia

gabapentin and pregabalin ADRs

HA, tremor | pregabalin- controlled substance b/c may induce euphoria

lamotrugine MOA

suppresses sustained rapid firing of neurons and produces volatage and use-dependent inactivation of NaChs inhibits V-CaChS

lamotrugine uses

adjunct when >2yrs old for partial seizures and generalized seizures monotherapy in adults for partial seizures, adjucnt for primary genrealized tonic-clonic also used for bipolar disorder

lamotrugine ADRs

nausea somnolence rash rare stevens-johnson syndrome

lamotrugine DDIs

may increase concentration with concurrent use of OBC as well as decrease OBC efficacy

levetiracetam MOA

binds selectively to synaptic vesicular protein modifies synaptic release of glutamate and GABA

levetiracetam uses

adjunct partial seizures in adults and kids primary generalized tonic-clonic seizures myoclonic seizures of juvenile myoclonic epilepsy

levetiracetam ADRs

less common more serious mood and behavioral changes

ethosuximide MOA

reduces the low T-type CaCH threshold (thalamic pace maker)

ethosuximide uses

absence seizures

ethosuximide ADRs

gastric distress

ethosuximide DDIs

valproic acid may inhibit meta or ethosuximide

valproic acid MOA

blocks sustained high frequency firing of neurons | action against partial seizures d/t effect on Na current via bockde of NMDARs

valproic acid PK

fully ionized at body pH | highly protein bound

valproic acid uses

``` absence seizures myoclonic seizures generalized tonic-clonic seizures partial seizures status epilepticus bipolar migraine prophylaxis ```

valproic acid ADRs

GI, heartburn fine tremor weight gain, increased appetite, hair loss hepatotoxic, thrombocytopenia *monitor

first line for partial seizures, including seondarily gerneralized

carbamazepine lamotrigine oxcarbazepine levetiracetam

first line for primary generalized tonic-clonic

valproate lamotrigine levetiracetam

first line for | absence seizures

ethosuximide | valproate

atypical absence, myocloinic, atonic

valproate lamotrigine levetiracetam

which drugs enhance NaCh inactivation?

``` carbamazepine phenytoin topiramate lamotrigine valproate zonisamide ```

which drugs enhance GABA synaptic transmission

vigabatrin and valproate (both decrease GABA breakdown in neuron) tiagabine (inhibit GABA transport out of cleft) benzodiazepines and barbituates (bind GABARs)

which drugs reduce Ca current?

valproate | ethosuzimide

Stevens-johnson syndrome

asians w/HLA-B1502

topiramate MOA

NaCh GABARs CaChs can also act on glutamate/NMDARs

topiramate uses

partial, generalized tonic-clonic, infantile spasms, absence seizures, migranes

topiramate ADRs

paresthesias nervousness weight loss

diazepam MOA

enhance GABA mediated Cl influx

diazepam MOA

extremely lipophillic

diazepam uses

status epliepticus myoclonic partial generalized tonic-clonic

phenobarbital MOA

enahances GABA mediates current and decrease glutamate release

phenobarbital P

hepatic enzyme inducer

phenobarbitol uses

partial seizues | generalized tonic-clonic

what drugs mess with OBC effectiveness

``` carbamazepine oxcarbamazepine phenobarbital phenytoin primidone ruginamide ```

which drugs are teratogenic

phenytoin valproate topiramate