Paper I
2021 December (Supplementary) (2010 Scheme) · 40 marks · 120 min

Question

Classify antiepileptic drugs. Explain the mechanism of action, uses and adverse effects of phenytoin and sodium valproate. List four drugs used in status epilepticus. (2+3+1)

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Answer

Classification of antiepileptic drugs

  • Hydantoins: Phenytoin
  • Barbiturates: Phenobarbitone
  • Iminostilbenes: Carbamazepine
  • Fatty acid derivatives: Sodium valproate
  • Succinimides: Ethosuximide
  • Newer agents: Lamotrigine, Levetiracetam, Gabapentin

Mechanism, uses and adverse effects of Phenytoin

  • Mechanism: Blocks voltage-gated sodium channels, prolonging their inactivated state, reducing sustained high-frequency repetitive neuronal firing
  • Uses: Partial and generalized tonic-clonic seizures, status epilepticus
  • Adverse effects: Gum hypertrophy, hirsutism, cerebellar signs (nystagmus, ataxia), megaloblastic anaemia, osteomalacia, Stevens-Johnson syndrome, fetal hydantoin syndrome, enzyme induction

Mechanism, uses and adverse effects of Sodium Valproate

  • Mechanism: Blocks sodium channels, increases GABA levels, blocks T-type calcium channels
  • Uses: Broad-spectrum — generalized tonic-clonic, absence, myoclonic seizures; bipolar disorder; migraine prophylaxis
  • Adverse effects: Hepatotoxicity, teratogenicity (neural tube defects), weight gain, tremor, alopecia, thrombocytopenia

Four drugs used in status epilepticus

  • Diazepam, Lorazepam, Phenytoin/Fosphenytoin, Phenobarbitone

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