CARBAMAZEPINE

  • Understand PK of carbamazepine.
Structure/Class
  1. Similar to TCA/Imipramine
Pharmacodynamics
  1. Similar to phenytoin
    • Na+ channel blockade. Inhibits repetitive high frequency neuronal firing.
    • Also may potentiate K+ channel, causing hyperpolarization.
Absorption/administration
  1. PO
    • Peak levels occur at 6 hours
Distribution
  1. Distributes slowly.
  2. Vd = 1L/kg,
  3. It is 70% bound to plasma proteins but there is no displacement of other drugs.
Metabolism
  1. Completely metabolized hepatically to carbamazepine 10,11 epoxide (it has anti-convulsant activity)
  2. Strong inducer of hepatic enzymes. May induce its own metabolism and may require frequent dose changes in the first few weeks of treatment.
Excretion
  1. Renal

 
Indications
  1. GTCS
  2. Trigeminal neuralgia
  3. Mania
Contraindications
Special precautions
Interactions
  1. Strong enzyme inducer and may also induce its own metabolism.
    • Other inducers, e.g. phenytoin/phenobarbital may decrease its level.
    • Other inhibitors (e.g.  valproate) may increase its levels.

 
Adverse events
  1. Side effects as follows:
    • CNS (most common) – diplopia and ataxia. Mild drowsiness.
    • GIT upset
    • Idiosyncratic à blood dyscrasias and aplastic anaemia.
    • Rash
Dosing/administration
Toxicology
Withdrawal syndrome
Special notes