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week 16: anti-epileptic drugs (AEDs)

Terms in this set (48)

What is Epilepsy?
Recurrent seizures unprovoked by acute systemic or neurological insults
What are the 3 main seizure classifications?
-focal
-generalized
-unknown
Seizures that start in one area of the brain are called what?
Focal
What are the 2 ways that focal seizures can present? Which kind can develop into bilateral (generalized) convulsions?
-can either retain awareness or have altered awareness
-altered awareness focal seizures can develop into bilateral convulsions
Seizure that involve both hemispheres of the brain are called what?
Generalized
The "unknown" classification of seizures includes what?
Epileptic spasm
What are the 6 types of generalize seizures?
-absence (can be atypical, myoclonic, or eyelid myoclonic)
-atonic
-tonic
-clonic
-tonic clonic
-myoclonic (can be atonic or tonic)
Status epilepticus is defined as either more than _____ minutes of continuous seizure activity OR ____ or more sequential seizures spanning this time frame without _______________ and a medical emergency often requiring _______________
more than 5 minutes of continuous seizure activity OR 2 or more sequential seizures spanning this time frame without full recovery in between and a medical emergency often requiring airway support
AEDs act by decreases the __________ and/or __________ of seizures in patients with epilepsy
frequency and/or severity
AEDs treat the __________ rather than the underlying condition
symptoms (i.e. treat seizures, not epilepsy)
Approximately what percent of all people with epilepsy can become seizure free with single drug therapy?
70%
*the 3 main modes of action of AEDs are to:
-[inc/dec] inward voltage-gated positive currents (___ and ___)
-[inc/dec] inhibitory neurotransmitter activity (_______)
-[inc/dec] excitatory neurotransmitter activity (________ and ________)
-dec inward voltage-gated positive currents (Na+ and Ca2+)
-inc inhibitory neurotransmitter activity (GABA)
-dec excitatory neurotransmitter activity (glutamate and aspartate)
What are some common side effects of AEDs?
-sedation
-cosmetic (gum hypertrophy)
-weight gain/loss
-reproductive function
-cognitive
-behavioral
-allergic
AEDs are primarily metabolized by _________ except for 5 AEDs that are ____________ instead. Name 3 common ones
-primarily hepatic metabolism
-renally excreted: gabapentin, pregabalin, and levetiracetam
Some medications compete for protein-binding sites of AEDs which can cause what?
Displace the bound AED and lead to inc. plasma concentration of that drug
What is the principle binding protein for AEDs?
Albumin
*some AEDs are potent inducers of what? why is this clinically important?
-inducer of hepatic microsomal enzymes
-may have increased dose requirements for thiopental, propofol, midazolam, opioids, and NDNMRs
*which group of drugs acts on GABA receptors to increase the frequency of Cl-channel openings?
Benzodiazepines
*which group of drugs acts on GABA receptors to increase the duration of Cl-channel openning?
Barbiturates
*which drug acts on GABA receptors to block GABA transaminase (inc. GABA levels by inhibiting its breakdown)?
Vigabatrin
*what AED acts as a AMPA receptor antagonist thereby blocking the glutamate site?
Topiramate (Topamax)
Describe Topiramate's (Topamax) target receptor(s), half-life, and use?
-antagonist at AMPA (glutamate) receptor but highly pleiotropic!
-long half-life (20 hrs)
-used for focal seizures (or as an adjunct for absence and tonic-clonic seizures)
*what receptor does felbamate (felbatol) act on?
Antagonsit at NMDA receptor (also modulates GABA-A receptors)
*what receptor has multiple potential target sites for AEDs?
GABA
*benzodiazepines bind ________ receptors and increase the _________ of Cl- channel opening
-GABA-A
-frequency
What 2 benzodiazepines are used as first line treatment for status epilepticus but have no indication for use as chronic AEDs?
Lorazepam (Ativan) and diazepam (valium)
What benzo is used as a 4th line AED for absence seizures and sometimes for myoclonic?
Clonazepam
*what type of drug is phenobarbital (donnatal) and therefore what effect does it have on GABA receptors?
Barbiturate; increases duration of Cl- channel opening
*what effect does phenobarbital (donnatal) have on p450?
Induces it
*describe the effect of phenytoin and carbamazepine on their target channel (which is what?) and what they are dependent on?
-block Na channels at high firing frequencies
-use-dependent (less effect on physiological neuronal firing than on seizure activity)
*what effect does phenytoin (dilantin) have on p450?
Induces it
*what is the prodrug for phenytoin?
Fosphenytoin
*what effect does carbamazepine (tegretol) have on p450?
Induces it
*What drug is pleiotropic and acts on glutamate receptors and Ca2+ channels?
Lamotrigine (lamictal)
*what drug acts specifically on T-type Ca2+ channels in the thalamus and is very effective against absence seizures?
Ethosuximide (emeside, zarontin)
*what is the half-life of Ethosuximide (emeside, zarontin)?
LONG! (40 hrs).. slowly titrate to effect
*does Ethosuximide (emeside, zarontin) cause high levels of sedation?
No! very low sedation
*what type of receptors does valproate/valproic acid (Depakote) act on and what effect does it have at these receptors?
K+ channels agonist: increases outward K+ currents
*what effect does valproate/valproic acid (Depakote) have on p450?
Inhibits it!
What 4 anesthetic agents can act as anti-convulsant? At high or low doses?
-LA's (low dose)
-benzos (any dose)
-propofol (high dose)
-ketamine (high dose)
Which 6 anesthetic agents can act as PRO-convulsant? At high or low dose?
-LA's (high dose)
-volatiles (sevo and des)
-propofol (low dose)
-opioids
-ketamine (low dose)
-etomidate
How should you treat seizures? (1st and 2nd line drugs)
1. Benzos: 4-8 mg diazepam or lorazepam (can give versed if on hand)
2. Give phenytoin, phenobarbital, valproic acid, or levetiracetam
Which AED is NOT metabolized by the liver?

A. Phenytoin
B. Valproic acid
C. Carbamazepine
D. Gabapentin
E. None of the above
D. Gabapentin
Which is NOT a potential mechanism of action for an AED?

A. Increase Na+ channel currents
B. Decrease glutamate activity
C. Increase GABA activity
D. Increase K+ channel currents
E. Increase mean Cl- channel opening duration
A. Increase Na+ channel currents
Ethosuximide is highly titratable because of its short half-life.

A. True
B. False
B. False
Benzodiazepines:

A. Increase the duration of Cl- channel opening
B. Bind to GABAB receptors
C. Are widely used for long-term epilepsy treatment
D. Cause minimal sedation
E. Are first line agents for status epilepticus
E. Are first line agents for status epilepticus
This AED inhibits p450:

A. Lorazepam
B. Phenytoin
C. Valproic acid
D. Carbamazepine
C. Valproic acid
Which of the following anesthetic agents are never pro-convulsant?

A. Local anesthetics
B. Propofol
C. Ketamine
D. Volatile anesthetics
E. None of the above
E. None of the above
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