THERAPEUTICS

Brands

• Tegretol
• Carbatrol
• Equetro
• see index for additional brand names

Generic?

• Yes (not for extended release formulation)

Class

• Anticonvulsant, antineuralgic for chronic pain, voltage-sensitive sodium channel antagonist

Commonly Prescribed for

• (bold for FDA approved)
• Partial seizures with complex symptomatology
• Generalized tonic-clonic seizures (grand mal)
• Mixed seizure patterns
• Pain associated with true trigeminal neuralgia
• Acute mania/mixed mania (Equetro)
• Glossopharyngeal neuralgia
• Bipolar depression
• Bipolar maintenance
• Psychosis, schizophrenia (adjunctive)

How The Drug Works

• Acts as a use-dependent blocker of voltage-sensitive sodium channels
• Interacts with the open channel conformation of voltage-sensitive sodium channels
• Interacts at a specific site of the alpha pore-forming subunit of voltage-sensitive sodium channels
• Inhibits release of glutamate

How Long Until It Works

• For acute mania, effects should occur within a few weeks
• May take several weeks to months to optimize an effect on mood stabilization
• Should reduce seizures by 2 weeks

If It Works

• The goal of treatment is complete remission of symptoms (e.g., seizures, mania, pain)
• Continue treatment until all symptoms are gone or until improvement is stable and then continue treating indefinitely as long as improvement persists
• Continue treatment indefinitely to avoid recurrence of mania and seizures
• Treatment of chronic neuropathic pain most often reduces but does not eliminate pain and is not a cure since symptoms usually recur after medicine stopped

If It Doesn’t Work (for bipolar disorder)

• Many patients only have a partial response where some symptoms are improved but others persist or continue to wax and wane without stabilization of mood
• Other patients may be nonresponders, sometimes called treatment-resistant or treatment-refractory
• Consider increasing dose, switching to another agent or adding an appropriate augmenting agent
• Consider adding psychotherapy
• Consider biofeedback or hypnosis for pain
• For bipolar disorder, consider the presence of noncompliance and counsel patient
• Switch to another mood stabilizer with fewer side effects or to extended release carbamazepine
• Consider evaluation for another diagnosis or for a comorbid condition (e.g., medical illness, substance abuse, etc.)

Best Augmenting Combos for Partial Response or Treatment-Resistance

• Lithium
• Atypical antipsychotics (especially risperidone, olanzapine, quetiapine, ziprasidone, and aripiprazole)
• Valproate (carbamazepine can decrease valproate levels)
• Lamotrigine (carbamazepine can decrease lamotrigine levels)
• Antidepressants (with caution because antidepressants can destabilize mood in some patients, including induction of rapid cycling or suicidal ideation; in particular consider bupropion; also SSRIs, SNRIs, others; generally avoid TCAs, MAOIs)

Tests

• Before starting: blood count, liver, kidney, and thyroid function tests
• During treatment: blood count every 2 to 4 weeks for 2 months, then every 3 to 6 months throughout treatment
• During treatment: liver, kidney, and thyroid function tests every 6–12 months
• Consider monitoring sodium levels because of possibility of hyponatremia
• Before starting: individuals with ancestry across broad areas of Asia should consider screening for the presence of HLA-B*1502 allele; those with HLA-B*1502 should not be treated with carbamazepine