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PR3153 > Neuropharmacology - Antiepileptics > Flashcards

Neuropharmacology - Antiepileptics Flashcards

1
Q

How do anti-epileptics work in general?

A
  • Decrease membrane excitability by altering Na+ and Ca2+ conductance during action potentials
  • Enhance effects of inhibitory neurotransmitters
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2
Q

Which anti-epileptic drugs are first line for newly diagnosed partial and generalised tonic clonic seizures?

A
  • Phenytoin
  • Carbamazepine
  • Valproate
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3
Q

What is the MOA of phenytoin?

A

Blocks voltage-dependent Na+ channels

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4
Q

What types of seizures is phenytoin suitable for?

A

All except absence seizures

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5
Q

Why does phenytoin require TDM?

A

Phenytoin exhibits non-linear dose-concentration relationship due to
- narrow therapeutic range (40-100uM)
- saturation kinetics

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6
Q

What types of seizures is carbamazepine suitable for?

A

All except absence seizures

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7
Q

What is the MOA of carbamazepine?

A

Blocks voltage-dependent Na+ channels

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8
Q

What are the special pharmacokinetic attributes of carbamazepine?

A

→ CYP450 inducer
→ T1/2 shortens w repeated doses – hepatic enzyme autoinduction (induces enzymes metabolising it)

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9
Q

What is the allele that predisposes patients taking carbamazepine to develop SJS?

A

HLA B*1502

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10
Q

What is the MOA of sodium valproate?

A

Blocks voltage-dependent Na+ and Ca2+ channels

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11
Q

What types of seizures is sodium valproate suitable for?

A

All

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12
Q

What is the special pharmacokinetic attribute of sodium valproate?

A

binds strongly to plasma proteins, to the extent of displacing all other anti-epileptics

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13
Q

What are the dose-related adverse effects and anti-epileptics in general?

A

drowsiness, confusion, nystagmus, ataxia, slurred speech, nausea, unusual behaviour, mental changes, coma

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14
Q

What are the non-dose-related adverse effects and anti-epileptics in general?

A

hirsutism, acne, gingival hyperplasia, folate deficiency, Osteomalacia, hypersensitivity reactions (incl SJS)

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15
Q

What is the MOA of the benzodiazepines?

A

Enhances binding of GABA to receptor coupled to Cl- channel, resulting in greater entry of Cl- ions to lead to hyperpolarization of cell

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16
Q

What type of benzodiazepine is diazepam?

A

Long-acting (1-3 days duration of action)

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17
Q

What are the possible unwanted effects of benzodiazepines?

A

Acute Toxicity/Overdose (esp w alcohol)

Side Effects
→ Drowsiness, confusion, amnesia
→ Impaired muscle coordination

Tolerance and Dependence

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18
Q

What is the antidote for benzodiazepine toxicity?

A

Flumazenil (benzodiazepine antagonist)

19
Q

What is the MOA of barbituates?

A

Also potentiate GABA-mediated Cl- currents, but at a site distinct from benzodiazepines
(ie flumazenil will not work here)

20
Q

What are barbituates used for?

A

Used as anti-epileptic for paediatric/neonatal pts (IV loading dose then IV or PO maintenance dose)

21
Q

What is the MOA of levetiracetam?

A

Unclear - apparently binds to synaptic vesicle protein 2A to protect against seizures

22
Q

What is levetiracetam used for?

A
  • Adjunct for partial onset seizures, myoclonic and primary generalized tonic-clonic seizure
  • Can be used as monotherapy for partial onset seizures in newly diagnosed epilepsy
23
Q

What are the pharmacokinetic attributes of levetiracetam?

A

→ Highly soluble and permeable
→ Linear PK w low intra and inter subject variability
→ Either IV or PO

24
Q

What are the common side effects of levetiracetam?

A

headache, vertigo, cough, depression, insomnia

25
Q

What are the rare (and serious) side effects of levetiracetam?

A

Agranulocytosis, suicide, delirium, dyskinesia

26
Q

What is the MOA of lamotrigine?

A
  • Blocks voltage-gated sodium channels
  • Inhibits release of glutamate
  • Impedes sustained repetitive neuronal depolarization
27
Q

What are the indications for lamotrigine?

A
  • Adjunctive Tx or monoTx of partial seizures and generalised seizures, incl tonic-clonic
  • MonoTx of typical absence seizure
28
Q

What are the PK attributes of lamotrigine?

A

→ Linear PK
→ PO
→ T1/2 is generally shorter in children
→ T1/2 is significantly reduced by coadministration w carbamazepine and phenytoin, increased by coadministration w valproate

29
Q

What are the common side effects of lamotrigine?

A

headache, irritability/aggression, tiredness

30
Q

What are the rare (and serious) side effects of lamotrigine?

A

agranulocytosis, hallucination, movement disorders (worsens PD), SJS/TEN, hepatic failure

31
Q

What is the MOA of topiramate?

A

Unclear, but seems to increase GABA activation of GABA-A receptors, enhance GABA induction of Cl- flux but does not inc channel opening time. May act on benzodiazepine-insensitive subtype of GABA-A receptors

32
Q

What are the indications for topiramate?

A
  • Indicated for monotherapy of partial seizures and generalised seizure, tonic clonic seizures
  • Adjunctive Tx for Lennox-Gastaut syndrome (severe childhood epilepsy)
  • Prophylaxis of migraine headaches in adults
33
Q

What are the pharmacokinetic attributes of topiramate?

A

→ Linear PK
→ PO
→ Long T1/2
→ Predominantly renal clearance, not a potent inducer of drug metabolizing enzymes

34
Q

What are the common side effects of topiramate?

A

depression, somnolence, fatigue, nausea, weight change

35
Q

What are the rare (and serious) side effects of topiramate?

A

neutropenia, mania, tremor, transient blindness, SJS/TEN, hepatic failure

36
Q

When are antiepileptic drug levels tested?

A
  • Assessment of compliance to drug Tx for refractory epilepsy
  • Assessment of Sx due to possible antiepileptic drug toxicity
  • Titration of phenytoin dose
37
Q

What are the chronic adverse effects of carbamazepine?

A

peripheral neuropathy, osteomalacia, suicidal ideation

38
Q

What is the chronic adverse effect of phenobarbital?

A

osteomalacia

39
Q

What are the chronic adverse effects of phenytoin?

A

gingival hyperplasia, hirsutism, peripheral neuropathy at high doses, osteomalacia

40
Q

What are the chronic adverse effects of valproate?

A

Alopecia, reversible weight gain, suicidal ideation

41
Q

What is the TDM reference range for phenytoin?

A

10-20mg/L

42
Q

What is the TDM reference range for valproate?

A

50-100mg/L

43
Q

What is the TDM reference range of carbamazepine?

A

4-12 mg/L

44
Q

What is the TDM reference range of phenobarbital?

A

15-40mg/L

PR3153 (16 decks)

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