What is the recommended dosing for Tegretol (carbamazepine)?

Tegretol (Carbamazepine) Dosing

For epilepsy in adults and children over 12 years, start with 200 mg twice daily (400 mg/day) and increase by up to 200 mg/day at weekly intervals until optimal response is achieved, with maintenance doses typically 800-1200 mg daily, not exceeding 1200 mg daily in most patients. 1

Initial Dosing by Age Group

Adults and Children Over 12 Years

• Starting dose: 200 mg twice daily (400 mg/day total) 1
• Titration: Increase by up to 200 mg/day at weekly intervals using three or four times daily dosing 1
• Maximum dose: 1000 mg/day for ages 12-15 years; 1200 mg/day for patients above 15 years 1
• Rare exceptions: Doses up to 1600 mg/day have been used in adults in rare instances 1
• Maintenance: 800-1200 mg daily after achieving control 1

Children 6-12 Years

• Starting dose: 100 mg twice daily (200 mg/day total) 1
• Titration: Increase by up to 100 mg/day at weekly intervals using three or four times daily dosing 1
• Maximum dose: Generally should not exceed 1000 mg/day 1
• Maintenance: 400-800 mg daily 1

Children Under 6 Years

• Starting dose: 10-20 mg/kg/day divided twice or three times daily 1
• Titration: Increase weekly to achieve optimal response, administered three or four times daily 1
• Maximum dose: 35 mg/kg/24 hours 1
• Important caveat: No safety recommendation can be made for doses above 35 mg/kg/24 hours 1

Dosing for Trigeminal Neuralgia

• Starting dose: 100 mg twice daily (200 mg/day total) 1
• Titration: May increase by up to 200 mg/day using increments of 100 mg every 12 hours as needed for pain control 1
• Maximum dose: 1200 mg/day 1
• Maintenance: 400-800 mg daily controls pain in most patients, though some require as little as 200 mg or as much as 1200 mg daily 1
• Reassessment: Attempt dose reduction or discontinuation at least every 3 months 1

Critical Dosing Principles

Gradual Titration is Essential

• Start low and go slow: Initial doses should be increased gradually over 1-2 weeks as tolerated to minimize side effects 2
• Common pitfall: Rapid dose escalation causes fatigue, dizziness, ataxia, double vision, nausea, and vomiting 2
• The slow titration approach reduces peak-dependent side effects and improves tolerance 3

Frequency of Administration

• Minimum frequency: At least two divided doses daily due to carbamazepine's relatively short half-life 2
• Rationale: Single daily dosing causes excessively high peak blood levels 2
• Standard regimen: Three or four times daily dosing during titration and maintenance 1
• Modified-release formulation: Tegretol CR 400 or Tegretol-XR allows twice-daily dosing with better tolerance and compliance 3, 4

Administration with Food

• All carbamazepine formulations should be taken with meals 1

Therapeutic Monitoring

Target Blood Levels

• Therapeutic range: 4-8 mcg/mL 5
• When to check: If satisfactory clinical response has not been achieved at appropriate doses 1
• Timing of blood draw: Trough levels immediately before the morning dose (12-16 hours after last dose, or 24 hours if once daily) 6
• Steady state: Wait at least 5 drug half-lives after any dose change before checking levels 6

Laboratory Monitoring Requirements

• Baseline: Complete blood count (CBC), liver function tests (AST, ALT, albumin), serum creatinine 6
• During initiation: CBC and liver function tests every 1-1.5 months until stable dose achieved 6
• During stable therapy: CBC and liver function tests every 1-3 months 6
• Critical threshold: If ALT/AST increases to more than three times upper limit of normal, stop carbamazepine and may reinstitute at lower dose after normalization 6

Special Populations and Considerations

Genetic Screening

• HLA-B*15:02 screening: Should be performed before initiating treatment, particularly in patients of Asian descent, to reduce risk of Stevens-Johnson syndrome 5

Combination Therapy

• When adding carbamazepine to existing anticonvulsant therapy, add gradually while maintaining or gradually decreasing other anticonvulsants 1
• Exception: Phenytoin may need to be increased due to drug interactions 1

Drug Interactions Affecting Dosing

• Enzyme-inducing drugs: May reduce carbamazepine levels by accelerating metabolism, requiring higher doses 5
• Isoniazid: Can increase carbamazepine levels, potentially causing toxicity and requiring dose reduction 5
• Carbamazepine significantly decreases levels of: Oral contraceptives, warfarin, and corticosteroids through hepatic enzyme induction 5

Modified-Release Formulations

Advantages of Tegretol CR/XR

• Improved absorption: Sustains stable absorption and reduces fluctuations in serum concentration 3
• Better tolerance: Permits higher total daily doses by reducing peak-dependent side effects 3
• Improved compliance: Less frequent daily doses (once or twice daily) 3, 4
• Conversion: Patients can be switched from multiple-daily-dose Tegretol to Tegretol-XR twice daily on a milligram-per-milligram basis from one day to the next 7

Efficacy Data

• Once daily dosing with modified-release carbamazepine is possible in the majority of patients receiving monotherapy 4
• Seizure control is similar between once and twice daily dosing with modified-release formulations 4
• Most patients (79%) prefer once daily dosing over twice daily dosing 4

Common Pitfalls to Avoid

• Rapid titration: Causes dose-dependent side effects including drowsiness, loss of coordination, and vertigo 8
• Inadequate monitoring: Aplastic anemia, though rare, is most likely to occur within the first 3-4 months and requires diligent hematologic monitoring 2
• Checking levels too soon: Drawing blood before steady state is reached or at non-trough times leads to misleading results 6
• Ignoring drug interactions: Failing to adjust monitoring frequency when adding interacting medications 5
• Overlooking genetic risk: Not screening Asian patients for HLA-B*15:02 before initiation 5