Pharmacology · MU Sofia

30. Antiepileptic drugs.

Covers antiepileptic drugs, also called anticonvulsants, starting with their classification into sodium channel blockers, calcium channel blockers and GABA enhancers. It then walks through pharmacodynamics, pharmacokinetics, side effects, drug interactions, therapeutic uses and safety in pregnancy and lactation, ending with recap questions.

Inside: 9 sections · 5 labelled pictures · 10 flashcards · 4 min

Topic 29 of 93 in the MU Sofia syllabus for Pharmacology (Medicine, Year 3). The free AceMed note covers it in 9 sections, about 454 words (4 min of reading), with 10 flashcards.

In this note

  1. Antiepileptic Drugs (AEDs)
  2. Classification
  3. Pharmacodynamics
  4. Pharmacokinetics
  5. Side Effects
  6. Drug Interactions
  7. Therapeutic Uses
  8. Safety in Pregnancy & Lactation
  9. Recap Questions

Antiepileptic Drugs (AEDs)

Antiepileptic drugs (AEDs), also known as anticonvulsants, are medications used to prevent and control seizures in individuals with epilepsy and other seizure disorders.

Classification

  • Sodium Channel Blockers: Phenytoin, Carbamazepine, Oxcarbazepine
  • Calcium Channel Blockers: Ethosuximide, Gabapentin, Valproate
  • GABA Enhancers: Phenobarbital, Benzodiazepines (Diazepam, Clonazepam), Tiagabine

Pharmacodynamics

  • Sodium Channel Blockers:
  • Stabilize neuronal membranes by inhibiting voltage-gated sodium channels, preventing repetitive firing.
  • Reduce neuronal excitability, decreasing seizure activity.
  • Calcium Channel Blockers:
  • Reduce neuronal excitability by inhibiting voltage-gated calcium channels.
  • Ethosuximide specifically blocks T-type calcium channels, making it effective for absence seizures.
  • GABA Enhancers:
  • Enhance inhibitory GABAergic activity by:
  • Increasing GABA receptor activity.
  • Inhibiting GABA reuptake (Tiagabine).
  • Preventing GABA degradation (Vigabatrin).
  • Increase neuronal inhibition, reducing seizure occurrence.

Pharmacokinetics

  • Sodium Channel Blockers:
  • Well absorbed orally, metabolized in the liver (CYP450 enzymes).
  • Excreted in urine.
  • Phenytoin can also be administered IV.
  • Highly protein-bound (~90%), readily crosses the blood-brain barrier.
  • Variable half-lives, requiring dose adjustments.
  • Calcium Channel Blockers:
  • Orally absorbed, with high bioavailability.
  • Gabapentin & Pregabalin are renally excreted unchanged.
  • Short half-lives, requiring multiple daily doses.
  • Ethosuximide has moderate protein binding and wide CNS distribution.
  • GABA Enhancers:
  • Phenobarbital & Benzodiazepines:
  • Administered orally, IV, or rectally (diazepam).
  • Metabolized in the liver.
  • Phenobarbital has a long half-life.
  • Benzodiazepines have intermediate to long half-lives.
  • Tiagabine:
  • Orally administered, metabolized in the liver, excreted in urine.
  • Vigabatrin:
  • Orally absorbed, not extensively metabolized, excreted unchanged in urine.
  • Long duration of action.

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