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60 Cards in this Set

  • Front
  • Back
What is the mechanism of phenytoin?
Frequency-dependent block of fast Na channels
What is phenytoin the 1st line drug for?
Simple partial seizures
Complex partial seizures
Primary generalized tonic/clonic seizures
Secondarily generalized clonic/tonic seizures
What is fosphenytoin?
Water soluble prodrug of phenytoin

NOTE: used because phenytoin is water insoluble @ neutral pH
What problem can arise w/ the I.V. formulation of phenytoin? Why?
Can cause muscle necrosis

It is highly alkaline
What are the kinetics of phenytoin?

Clearance decreases as concentration increases
Some key phenytoin side effects (7)
Rashes (S-J syndrome)
Gingival hyperplasia
Neuro problems
What effects can phenytoin have on fetuses?

Cleft lip/palate
Cardiac malformation
How does phenytoin affect bone or platelet hemostasis?
Increases metabolism of vitamins D and K
Can cause osteoporosis and hypothrombinemia
When do idiosyncratic side effects of phenytoin usually show up?

What are they?
Usually within the first 3 months

Rashes, S-J syndrome, hepatitis, lymphadenopathy
What is dilantin?
The controlled relase formulation of phenytoin

NOTE: oral absorption of phenytoin is slow and variable
NOTE: there is large variation in phenytoin half-life
What is the mechanism of lamotigrine?
Frequency dependent Na channel blockade (like phenytoin)

PLUS, K channel activity in dendrites
What two drugs are used in Lennox-Gastault syndrome?
How is lamotigrine administered?
Oral formulation ONLY

It is given TWICE DAILY
What drug interactions does lamotigrine have?
Valproic acid inhibits its metabolism
What is a serious potential side effect of lamotigrine?
Terrible rash
(worse when on valproic acid as well)
What is the mechanism of topiramate?
Blocks glutamate receptors
Enhances GABA-mediated inhibition
How is topiramate metabolized?
Partially by liver (33%)
Rest is excreted unchanged
How is topiramate administered?
Topiramate's main side effects (4)
Difficulty concentrating
Memory problems

NOTE: in some pts. can cause weight loss, kidney stones, glaucoma, myopia
How bound to plasma proteins is topiramate?
Not much, only 15%
What are the mechanisms of valproate (4)?
Slows rate of Na channel reactivation
Effect on T-type Ca channels
Increases GABA levels
May activate K conductance
What is valproate the 1st line drug for?
Pts. who have BOTH absence and convulsive seizures
How bound to plasma proteins is valproate?
Causes it to have a low Vd
What idiosyncratic reaction of valproate is particularly dangerous?

When is it most common?
Fulminant hepatitis

In pts. < 2 y.o. on multiple agents
What drug may prevent the dangerous idiosyncratic side effect of valproate?
When is felbamate used?
REFRACTORY tonic, atonic, and absence seizures

REFRACTORY partial seizures
What side effects of felbamate have limited its use (2)?
Aplastic anemia
Hepatotoxicity (potentially fatal)
What drugs may be used against both partial and general seizures (5)?
What is the mechanism of carbamazepine?
Same as phenytoin
When is carbamazepine contraindicated?
In absence seizures
(may make these worse)
What is the primary treatment for trigeminal/glossop. neuralgia?
What is carbamazepine structurally related to?
How is carbamazepine metabolized?
In liver
It induces its own metabolism over 2-4 weeks
What is 10,11 epoxide?
The active metabolite of carbamazepine

Respsonible for the toxic adverse effects
What drugs inhibit the metabolism of carbamazepine (3)?
Ca channel blockers
Chronic use of carbamazepine can cause what serious side effects (2)?
Aplastic anemia
How is oxcarbamazepine different than carbamazepine?
Higher doses may be tolerated
Administered twice a day (instead of thrice)
LESS hepatic enzyme induction

Does NOT get metabolized into epoxide

NOTE: costs A LOT more
What is levetiracetam mainly used for?
Add on therapy for refractory partial seizures

2nd line therapy for partial seizures
How are the pharmacokinetics of levetiracetam?
Steady state is achieved in 2 days

NOT protein bound
NOT metabolized by liver
How is levetiracetam metabolized?
NOT by liver
66% is excreted unchanged
What is the cheapest anti-convulsant available?
What is primidone?
Prodrug that is metabolized into phenobarbital
What does phenobarbital have in common w/ carbamazepine?
BOTH may worse absence seizures
What are the only 4 BDZs approved to treat convulsive disorders?
Lorazepam, Diazepam (for status epilepticus)
Clorazepate, Clonazepam (for long-term treatment)
What is the mechanism for tiagabine?
Inhibits GABA-reuptake
When is tiagabine contraindicated?
In primary generalized seizures
(can result in status epilepticus)
What side effects does tiagabine cause?
Those of phenytoin
PLUS, tremor and depression
What is the mechanism of Gabapentin?
Modulates GABA synthesizing enzymes
How is gabapentin metabolized?

Excreted renally
What is gabapentin most commonly used for?
Treatment of neuropathic pain

It is effective in partial seizures ONLY when used in combos
What drugs can treat ONLY partial seizures?
What types of currents are needed to generate an absence seizure?
Low threshold T-type Ca currents
What is mechanism of ethosuxamide?
Blocks T-type Ca channels
What is ethosuxamide used for?
Pure absence seizures only
How is ethosuxamide administered?
Orally only
How is ethosuxamide metabolized?
75% hepatic
25% excreted unchanged
Behavioral disturbances due to ethosuxamide more common in what pts.?
Pts. w/ a history of some psychotic disturbance
What is status epilepticus?
Prolonged or repeated seizures w/o recovery of consciousness
Steps of treatment of status epilepticus
Ensure airway protection
I.V. glucose and thiamine
I.V. Lorazepam

Start fosphenytoin I.V. over 20 - 30 mins
If ineffective, try phenobarbital
If ineffective, use anesthetics
When should treatment for status epilepticus being
BEFORE patient even arrive in the ER