carbamazepine

Class




  • Antiepileptic drug (AED)




Carbamazepine


Commonly Prescribed for


(FDA approved in bold)



  • Complex partial seizures with or without secondary generalization (adults and children, monotherapy and adjunctive)
  • Generalized tonic-clonic seizures
  • Mixed seizure patterns
  • Trigeminal neuralgia
  • Glossopharyngeal neuralgia
  • Lennox-Gastaut syndrome
  • Temporal lobe epilepsy (children and adults)
  • Neuropathic pain
  • Alcohol withdrawal
  • Restless legs syndrome
  • Bipolar I Disorder (acute manic and mixed episodes)
  • Psychosis/Schizophrenia (adjunctive)



Carbamazepine


How the Drug Works



  • Blocks voltage-dependent sodium channels
  • Modulates sodium and calcium channels and GABA and glutamate transmission



Carbamazepine


How Long Until It Works



  • Seizures – 2 weeks or less
  • Trigeminal neuralgia or neuropathic pain – hours to weeks
  • Mania – weeks



Carbamazepine


If It Works



  • Seizures – goal is the remission of seizures. Continue as long as effective and well-tolerated. Consider tapering and slowly stopping after 2 years without seizures, depending on the type of epilepsy
  • Trigeminal neuralgia – should dramatically reduce or eliminate attacks, pain may recur. Periodically attempt to reduce to lowest effective dose or discontinue



Carbamazepine


If It Doesn’t Work



  • Increase to highest tolerated dose. Subject to autoinduction, meaning that dose requirements can change over time
  • Epilepsy: consider changing to another agent, adding a second agent or referral for epilepsy surgery evaluation. Check level if compliance is in question. When adding a second agent, keep drug interactions in mind
  • Trigeminal neuralgia: Try an alternative agent. For truly refractory patients referral to tertiary headache center, consider surgical or other procedures



Carbamazepine


Best Augmenting Combos for Partial Response or Treatment-Resistance



  • Epilepsy: drug interactions can complicate multi-drug therapy
  • Pain: Can combine with other AEDs (gabapentin or pregabalin) or tricyclic antidepressants



Carbamazepine


Tests



  • Baseline CBC, liver, kidney, and thyroid tests
  • Check CBC biweekly for 2 months then every 3 months
  • Liver, kidney, and thyroid tests every 6–12 months
  • Check sodium levels for symptoms of hyponatremia



Adverse Effects (AEs)




Carbamazepine


How Drug Causes AEs



  • CNS AEs are probably caused by sodium channel blockade effects
  • Mild anticholinergic side effects



Carbamazepine


Notable AEs



  • Sedation, dizziness, ataxia, headache, nystagmus
  • Nausea, vomiting, abdominal pain, constipation, pancreatitis, loss of sex drive
  • Aching joints and leg cramps
  • Elevated liver enzymes
  • Benign leukopenia (transient; in up to 10%)



Carbamazepine


Life-Threatening or Dangerous AEs



  • Rare blood dyscrasias: aplastic anemia, agranulocytosis
  • Dermatologic reactions including toxic epidermal necrolysis and Stevens-Johnson syndrome. (More common in Asian patients.) Can aggravate rash of lupus
  • Can reduce thyroid function
  • Hyponatremia/SIADH (syndrome of inappropriate antidiuretic hormone secretion)
  • May increase seizure frequency in patients with generalized seizure disorders



Carbamazepine


Weight Gain



  • Not unusual



Carbamazepine


Sedation



  • Problematic


  • May limit use



Carbamazepine


What to Do About AEs



  • Take with food, split dose, and take higher dose at night to improve tolerability
  • Extended-release form may be better tolerated
  • Rashes are common but usually not severe. Usually resolves with time or decreased dose. If severe stop drug. Do HLA typing prior to use in Asian patients
  • Elevated liver enzymes usually resolve spontaneously

Feb 16, 2017 | Posted by in PHARMACY | Comments Off on carbamazepine

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