Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
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?
|
NON-linear
Clearance decreases as concentration increases |
|
|
Some key phenytoin side effects (7)
|
Nystagmus
Rashes (S-J syndrome) Hepatitis Lymphadenopathy Gingival hyperplasia Hirsutism Neuro problems |
|
|
What effects can phenytoin have on fetuses?
|
Teratogenic
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?
|
Lamotigrine
Topiramate |
|
|
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?
|
Orally
TWICE DAILY |
|
|
Topiramate's main side effects (4)
|
Anxiety
Agitation 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?
|
Extensively
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?
|
L-carnitine
|
|
|
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)?
|
Phenytoin
Lamotigrine Topiramate Valproate Felbamate |
|
|
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?
|
Carbamazepine
|
|
|
What is carbamazepine structurally related to?
|
TCAs
|
|
|
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)?
|
Macrolides
Cimetidine Ca channel blockers |
|
|
Chronic use of carbamazepine can cause what serious side effects (2)?
|
Leukopenia
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?
|
Linear
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?
|
Phenobarbital
Primidone |
|
|
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?
|
NO METABOLISM
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?
|
Gabapentin
Tiagabine Carbamazepine Oxcarbamazepine Levetiracetam |
|
|
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
|
