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CPPS 306 > Chapter 21: AEDs, Anticonvulsants > Flashcards

Chapter 21: AEDs, Anticonvulsants Flashcards

1
Q

What does it mean when it is said that siezures have a bimodal distribution?

A

More common in early childhood and in the elderly.

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2
Q

What is a seizure?

A

Sudden, excessive, and synchronous discharges of neurons.

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3
Q

What can seizures result in?

A
  • Transient loss of consiousness
  • Abnormal movements
  • Atypical or odd behavior
  • Distorted perception
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4
Q

What are the the two types of seizures?

A
  1. Partial (Affects a localized area of the brain initially)
  2. Generalized (Involves both hemispheres from the start; No Aura/Warning Signs)
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5
Q

What are the main differences between partial and generalized seizures in regards to treatment?

A

Partial - All AEDs are effective except ethosuximide.

Generalized - AED options are more limited.

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6
Q

What are the types of Partial seizures.

A

Simple Partial: Sensory changes or auras without loss of awareness.

Complex Partial: Impaired awareness, often involving the temporal lobe.

Secondarily Generalized: Starts as a focal seizure but spreads to involve both hemispheres.

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7
Q

What are the types of Generalized seizures?

A

Generalized Tonic-Clonic (GTC): Stiffening and jerking of muscles.

Tonic/Atonic: Sudden stiffening (tonic) or loss of muscle tone (atonic).

Absence: Brief episodes of staring or loss of awareness.

Myoclonic: Sudden, quick muscle jerks.

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8
Q

What are the Mechanisms of action to target with anti convulsants?

A
  1. Voltage-Gated Na Channels
  2. Potentiation of GABAergic mechanisms
  3. Blockade of Ca Channels
  4. Blockade of glutamate receptor channels (NMDA, AMPA)
  5. Opening of voltage-gated K channels
  6. Antagonism of Exocytosis.
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9
Q

What are the drugs that target Voltage gated Na channels?

A
  • Phenytoin
  • Carbamazepine
  • Oxcarbazepine
  • Lamotrigine
  • Phenobarbital (Higher Doses)
  • Valproic Acid (Higher Doses)

These drugs prolong the inactivation state of Na channels.

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10
Q

What are the pharmacokinetics of Phenytoin?

A
  • Zero order kinetics (Drug metabolism gets saturated) - Watch dose
  • p450 metabolism - beware of toxicity
  • Enzyme Inducer
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11
Q

What are the pharmacokinetics of Carbamazepine/Oxcarbazepine?

A
  • P450 Metabolism
  • Enzyme Inducer (Less so for oxcarb)
  • Induces its own metabolism
  • Dose adjustment is required
  • May lower other medication levels (oral contraceptives)
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12
Q

What are the pharmacokinetics of Lamotrigine?

A
  • Metabolized by glucoronic acid conjugation.
  • If combined with valproic acid (VPA), slowly increase VPA to avoid toxicity/side effects
  • VPA ↓s metabolism (glucuronidation) resulting in 2-fold ↑ in lamotrigine half-life
  • Levels ↓ significantly in pregnancy or with oral contraceptive as glucuronidation is induced by estrogen -> Increased dose required
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13
Q

What are the pharmacokinetics of Valproic Acid?

A
  • Heavy protein binding → displaces other protein bound medications → toxicity (e.g. with phenytoin)
  • Blocks liver metabolism → ↑ Lamotrigine, Phenobarbital levels
  • VPA level is decreased by P450 inducers (e.g. phenytoin)
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14
Q

What are all the different ways to potentiate GABA to increase inhbition and the drugs involved in each?

A

Increase Duration of Cl- channel opening: Phenobarbital
Increase Frequency of Cl- channel opening: **Benzodiazepines
**
Felbamate, Topiramate, and Valproic Acid may have similar effect (not their main mechanism of action)

Blockade of GABA degradation by GABA transaminase (GABA-T) blockade:
Vigabatrin
** Valproic acid** at high concentrations

Blockade of GABA transporter (GAT-1) in neurons and glial cells:
Tiagabine

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15
Q

What are the different Benzodiazepines used to treat seizures and epilepsy?

A

Lorazepam and Midazolam -> Used in emergency situations intravenously. (Loraepam can be used sublingualy by patient at aura to avoid seizure generalization)

Diazepam - Rectal -> Used in children by parents at home to stop seizures.

Clobazam -> Used as adjunctive AED long term seizure treatment.

Benzodiazepine withdrawal may cause seizures in non epileptic persons.

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16
Q

What two drugs increae GABA in the ECF?

A

* Vigabatrin inhibits GABA transaminase
* Tiagabine inhibits GABA transporters

17
Q

What are the drugs that block Ca channels?

A

Ethosuximide, Valproic Acid -> Block Low Threshold T-Type Ca channels in the thalamus, the pacemaker **for absence seizures. **

Gabapentin, Pregabalin -> *Block Pre-synaptic V-gated Ca channels. *

18
Q

Explain the mechanism of how GABApentin and Pregabalin work.

A
  • molecular structure similar to GABA but no direct activation of receptor
  • Bind to α2δ subunit of presynaptic voltage dependent Ca2+ channel → ↓ Ca2+ entry → ↓ excitatory neurotransmitter Glutamate release
19
Q

What drugs use glutumate antagonism to treat seizures?

A

Phenobarbital
Felbamate: NMDA blocker
Topiramate: AMPA blocker
Perampanel: AMPA blocker

20
Q

What drugs increae K channel permeability?

A

Valproic Acid

Ezogabine

21
Q

What drugs use exocytosis antagonism?

A

Levetiracetam

22
Q

How does Levetiracetam work and what are the adverse effects?

A

Mechanism: Binding to SV2A synaptic vesicle protein →↓ stimulatory neurotransmitter release

Adverse Effects: Depression, Suicidal Ideas, Aggression.

23
Q

Most anticonvulsants metabolized by hepatic enzymes;

Except?

A
  • Gabapentin
  • Pregabalin
  • Vigabatrin
  • Levetiracetam

These are excreted by the kidney.

24
Q

What are 3 mechanisms of drug interactions with anticonvulsants?

A

By **blocking antiseizure drug metabolism **

By displacing the drugs from plasma proteins binding sites -> Increased Potency (Valproic Acid increases Phenytonin Levels)

Induction of antiseizure drug metabolism (e.g. by Rifamipin, or some antiseizure meds themselves)
- Carbamazepine (CBZ) induces its own metabolism, lowering its levels over time.

25
Q

What are all the P450 inducers?

A
  • Phenytoin
  • Phenobarbital
  • Carbamazepine
26
Q

What are all the effects of P450 enzyme inducers?

A
  • Decreased levels of other drugs:
    Drugs metabolized by the P450 system (e.g., statins in elderly patients) may have reduced efficacy.
  • Decreased active Vitamin D levels:
    Leads to lower calcium absorption, increasing the risk of osteoporosis.
  • Reduced efficacy of oral contraceptives:
    May lead to contraceptive failure.
27
Q

What does Valproic acid do to Lamotrigine?

A

It blocks liver metabolism leading to increase Lamotrigine Levels.

28
Q

What things would make the ideal antiepileptic treatment?

A

CPPS 306 (11 decks)

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