Clinical Overview
Carbamazepine is an anticonvulsant with mood-stabilizing properties indicated for epilepsy, trigeminal neuralgia, and bipolar disorder. It is particularly effective for mixed episodes and rapid cycling bipolar disorder, and serves as an alternative to lithium for patients who cannot tolerate or do not respond to first-line mood stabilizers.
Primary Clinical Applications
Carbamazepine is indicated for partial seizures, generalized tonic-clonic seizures, trigeminal neuralgia, and acute manic or mixed episodes of bipolar I disorder (Equetro formulation). It may be particularly useful for bipolar patients with rapid cycling, mixed states, or comorbid substance abuse.
Mechanism and Clinical Benefits
Carbamazepine blocks voltage-gated sodium channels and has multiple other mechanisms including effects on calcium channels and neurotransmitter systems. Its mood-stabilizing effects may be related to kindling suppression and membrane stabilization, making it effective for both manic and depressive episodes.
Monitoring Requirements
Carbamazepine requires regular monitoring due to potential for serious blood dyscrasias, hepatotoxicity, and significant drug interactions through CYP enzyme induction. Genetic testing for HLA-B*1502 allele is recommended in Asian populations due to increased risk of Stevens-Johnson syndrome.
Prescribing Information
Dosing & Administration
Epilepsy – Adults:
- Initial: 200 mg twice daily (immediate release)
- Titration: Increase by 200 mg weekly
- Maintenance: 800-1200 mg daily in divided doses
- Maximum: 1600 mg daily
Bipolar Disorder (Equetro) – Adults:
- Initial: 200 mg twice daily
- Titration: Increase by 200 mg daily every few days
- Range: 400-1600 mg daily
- Target level: 4-12 mcg/mL
Trigeminal Neuralgia:
- Initial: 100 mg twice daily
- Titration: Increase by 100 mg every 12 hours
- Maintenance: 400-800 mg daily
Administration:
- Take with food to reduce GI upset
- Extended-release: Swallow whole, do not crush
- Divide immediate-release doses 2-4 times daily
Indications
- Partial seizures with complex symptomatology
- Generalized tonic-clonic seizures
- Mixed seizure patterns
- Trigeminal neuralgia
- Acute manic and mixed episodes of bipolar I disorder (Equetro)
Contraindications
- Hypersensitivity to carbamazepine or tricyclic compounds
- History of bone marrow depression
- Use with MAOIs (within 14 days)
- HLA-B1502 allele (Asian ancestry) – increased SJS/TEN risk
Warnings & Precautions
- Boxed Warning: Serious dermatologic reactions (SJS/TEN), aplastic anemia, agranulocytosis
- Blood dyscrasias: Monitor CBC regularly, especially first few months
- Dermatologic reactions: Discontinue immediately if rash develops
- Hyponatremia: Monitor sodium levels, especially in elderly
- Suicidal thoughts: Monitor for behavioral changes
- Drug interactions: Potent CYP3A4 inducer affects many medications
Drug Interactions
- CYP3A4 substrates: Carbamazepine decreases levels of many drugs
- Oral contraceptives: Reduced effectiveness
- Warfarin: Decreased anticoagulant effect
- Other anticonvulsants: Complex bidirectional interactions
- CYP3A4 inhibitors: Increase carbamazepine levels
Adverse Reactions
Common (>10%):
- Dizziness, drowsiness, ataxia, nausea, vomiting
Serious:
- Stevens-Johnson syndrome, aplastic anemia, agranulocytosis
- Hepatotoxicity, hyponatremia
Special Populations
- Asian ancestry: Screen for HLA-B1502 allele before initiating
- Pregnancy: Category D – risk of neural tube defects
- Hepatic/Renal Impairment: Use caution, monitor closely
- Monitoring: CBC, LFTs, sodium, drug levels (4-12 mcg/mL)
Medical Disclaimer: This information is for educational purposes only and is not intended as medical advice. Always consult with qualified healthcare professionals before making any treatment decisions. Individual patient circumstances may vary significantly.
