Antiseizure Drugs Flashcards Preview

Neurology > Antiseizure Drugs > Flashcards

Flashcards in Antiseizure Drugs Deck (30):
1

Which antiseizure medication is excreted in the urine largely unchanged?

Gabapentin

A image thumb
2

Which antiseizure medication is bound to plasma proteins the least?

Gabapentin

A image thumb
3

Phenytoin

  • Mechanism of Action: 
  • Pharmacokinetics: 

  • MECHANISM OF ACTION:
    • Alters Na ion conductance
      • Use dependent effect on sodium channels
    • Inhibits the generation of repetitive action potentials
  • PHARMACOKINETICS:
    • Dependent upon drug formulation
    • Highly protein bound
    • Pharmacokinetics are dose-dependent
    • Usual therapeutic level – 10 -20 μg/ml

4

What are the clinical uses of phenytoin?

  • Generalized tonic-clonic seizures
  • Partial seizures
    • ​NOT absence seizures

5

Phenytoin

  • Drug Interactions
  • Toxicity

  • Drug interactions
    • drugs metabolized by microsomal enzymes 
    • drugs that are protein bound
  • Toxicity
    • CNS (Dose-dependent) – nausea, anorexia, apathy, sedation, ataxia, nystagmus and diplopia.
    • Gingival hyperplasia
    • Hirsuitism
    • Teratogenicity -fetal hydantoin syndrome-cardiac defects, cleft palate
    • Hypersensitivity reactions - Rash

6

Which of the toxicities caused by phenytoin is not dose dependent?

  • gingival hyperplasia
  • hypersensitivity reaction (rash)

7

What is fosphenytoin and when is it used?

  • Water soluble phenytoin analog
  • Used IV in status epilepticus

8

Carbamazepine

  • Mechanism of Action 
  • Pharmacokinetics
  • Clinical Use

  • Mechanism of Action (similar to phenytoin)
    • blocks Na channels
    • does not interact with GABA
  • Pharmacokinetics
    • unpredictable absorption
    • hepatic enzyme induction
  • Clinical Use
    • drug of choice for partial seizures
    • contraindicated in absence seizures

9

Carbamazepine

Toxicity

Dose related

  • diplopia and ataxia
  • GI upset
  • drowsiness
  • rare blood discrasias
  • teratogen
    • increased incidence of Spinal Bifida
    • risk is less than with valproic acid

10

What is oxcarbazepine?

  • Newer analog
  • Similar in action, but less likely to cause CNS side effects
  • Less enzyme induction than carbamazepine

11

Ethosuximide

  • Mechanism of Action 
  • Pharmacokinetics 

  • Mechanism of Action 
    • Reduces low-threshold (T type) Ca currents in thalamic nuclei
  • Pharmacokinetics 
    • Well absorbed after oral administration
    • Not protein bound
      • Volume of distribution approximaes total body water
    • Liver metabolism (inhibited by valproic acid)
    • Long half life

12

What are the side effects/toxicity of ethosuximide?

  • Gastric distress (dose twice daily)
  • Lethargy & fatigue

13

Valproic Acid

  • Mechanism of Action
  • Pharmacokinetics

  • Mechanism of Action
    • Blocks repetitive neuronal firing
    • May reduce T-type Ca2+ currents
    • Increases GABA concentrations
  • ​Pharmacokinetics
    • Bound to plasma protein
      • competes with phenytoin
    • Distributes to ECF
    • Inhibits metabolism of phenobarbital, phenytoin and carbamazepine

14

Valproic Acid

  • Clinical Uses
  • Side Effects & Toxicity

  • Clinical Use
    • Absence seizures
    • Absence seizures w/ concomitant-generalized tonic-clonic seizures
    • Generalized tonic-clonic seizures and partial seizures
    • Myoclonic seizures
  • Side Effects & Toxicity
    • GI upset
    • weight gain, hair loss
    • idiosyncratic hepatotoxicity
    • teratogen – spinal bifida

15

What side effects/toxicity caused by valporic acid are not dose-related?

  • idiosyncratic hepatotoxicity
  • teratogenicity 

16

Felbamate

  • Mechanism of Action 
  • Clinical Use 
  • Side effects & Toxicity

  • Mechanism of Action 
    • Acts at the glycine modulatory site on the N-methyl-d-aspartate receptor -Antagonist
    • Also potentiates GABA
  • Clinical Use 
    • Partial seizures that are refractory to other agents
  • Side effects & Toxicity
    • aplastic anemia and hepatic failure 

17

Gabapentin (Neurontin®)

  • Structure: 
  • Pharamcokinetics: 
  • Clinical Uses:

  • Structural analog of GABA
    • Role of GABA in its action is not clear
    • It is not a GABA agonist
  • Pharmacokinetics:
    • Gabapentin is not metabolized and has no protein binding
    • devoid of the usual drug interactions
  • Clincial Uses:
    • Adjunct therapy in the treatment of partial seizures with or without secondarily generalized tonic-clonic seizures.
    • Also used for neuropathic pain and ALS

18

Pregabalin (Lyrica®)

  • Structure: 
  • Clinical Uses: 
  • Abuse potential?

  • Structurally similar to gabapentin but more potent
    • May interact with alpha 2 -delta subunit of voltage-gated calcium channels reducing neurotransmitter release
  • Clinical Uses:
    • Adjunctive therapy for partial seizures
    • Management of neuropathic pain associated with diabetic peripheral neuropathy and postherpetic neuralgia and fibromyalgia
  • DEA Schedule 5 drug - very limited abuse potential

19

Lamotrigine (Lamictal®)

  • Mechanism of Action: 
  • Clinical Uses: 
  • Pharmacokinetics: 
  • Side effects/toxicity:

  • Mechanism of Action:
    • Blocks repetitive action potentials
    • may block Na+ channels
  • Clincal Uses:
    • Used for partial, generalized tonic-clonic and absence (Not FDA approved) seizures including monotherapy
    • Approved for bipolar disorder
  • Pharmacokinetics:
    • Does not interfere with pharmacokinetics of other drugs
  • Side effects/toxicity:
    • May cause serious rash including Stevens-Johnson syndrome

20

Topiramate

  • Structure: 
  • Mechanism of Action: 
  • Clinical Uses: 
  • Side effects/toxicity:

  • Structure:
    • Derived from D-fructose
  • Mechanism of Action:
    • Inhibits excitatory transmission by antagonizing the ability of excitatory amino acids to activate the kainate/AMPA subtype of glutamate receptor
    • Blocks the spread of seizures rather than raise the seizure threshold
    • May also block sodium channels similar to phenytoin
  • Clinical Uses: 
    • add-on therapy of adults with partial seizures
    • Also used for prevention of migraines
  • Side effects:
    • fatigue, nausea, and confusion
    • weight loss 

21

Tiagabine

  • How does it work?
  • What is its clincal use? 
  • What are the adverse effects?

  • Inhibits the GABA transporter, GAT-1
    • thus inhibits reuptake of GABA
    • increased GABA in synapse
  • Is an effective add-on treatment for both complex and simple partial seizures
  • Adverse effects:
    • dizziness, tremor and somnolence

22

Levtiracetam

  • What are the clincal uses and side effects?

  • Used as adjunctive therapy for partial seizures
  • Also indicated for adjunctive treatment of myoclonic seizures and primary generalized tonic-clonic
  • Side effects:
    • somnolence, asthenia and dizziness

23

  • Which anti-seizure drug acts on both Na and Ca channels (T-type currents)?
  • What type of Ca channels?
  • How does this drug help with seizures?

  • Zonisamide (Zonegran®)
  • It reduces the voltage-dependent transient inward currents 
  • Stops the spread of seizures and suppresses their focus

24

What are the clinical uses and side effects of zonisamide?

  • CNS adverse reactions:
    • ataxia, anorexia, nervousness, fatigue and speech impairment 
  • Approved for adjunctive treatment of adults with partial seizures

25

Vigabatrin (Sabril®)

  • Mechanism of Action: 
  • Clinical Uses: 
  • Side effects/toxicity:

  • Acts by irreversibly inhibiting GABA metabolism 
    • GABA-Transaminase inhibitor
  • Approved for adjunctive treatment of refractory complex partial seizures and infantile spasms
  • Possible permanent effects on vision.

26

What drug is used in adjuntive treatment for Lennox-Gastaut syndrome?

Clobazam (Onfi®)

  • Blocks voltage-dependent sodium and calcium channels

27

What drug enhances slow inactivation of voltage-gated sodium channels?

Lacosamide (Vimpat®)

28

List drugs used for partial or secondarily generalized ACD’s (4):

  • carbamazepine
  • oxcarbazepine
  • phenytoin
  • (gabapentin)?

29

List drugs for Partial, Generalized, Secondary Gen,  or Multifocal ACD’s (8):

  1. valproic acid
  2. lamotrigine
  3. topiramate
  4. zonisamide
  5. levetiracetam
  6. felbatol
  7. rufinamide
  8. lacosamide

30

List drugs used for Absence seizures (3):

  1. ethosuximide
  2. valproic acid
  3. lamotrigine