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Medicines Monitoring

Carbamazepine monitoring

Published
Topics: CarbamazepineMonitoring
Using this page · Individualise medicines monitoring

This medicines monitoring page has been written using publications and expert opinion. It is designed to save clinician time, but not replace professional responsibility. When using this page you should: ensure an individualised monitoring plan is developed in partnership with the patient and take account of any locally agreed advice and guidance.

Contents
  1. Before starting
    1. Required
    2. Consider
  2. After started or dose changed
    1. Required
    2. Consider
    3. Hypothyroid patients
  3. Ongoing once stable
    1. Required
    2. Consider
  4. Abnormal results
    1. Leucopenia
    2. Full blood count
    3. Hepatic function
    4. Sodium
  5. Notes
    1. Advice to patients
    2. Interpreting carbamazepine levels
  6. Bibliography

Before starting

Required

  • Baseline
    • Body mass index
    • Full blood count
    • Liver function tests
    • Urea and electrolytes
    • Serum creatinine (for creatinine clearance) or Estimated glomerular filtration rate

Consider

  • Baseline
    • HLAB* 1502 alleleif Han Chinese or Thai origin patient
    • ECGif cardiovascular disease risk factors or disease

Han Chinese or Thai patients

Avoid carbamazepine unless essential in Han Chinese or Thai patients who possess the HLAB* 1502 allele, since these patients may be at an increased risk of Stevens-Johnson syndrome.

After started or dose changed

Required

  • At 2 weeks
    • Plasma carbamazepine concentrationtake blood immediately before next dose (trough level)
  • At 6 months
    • Full blood count
    • Urea and electrolytes
    • Liver function tests
    • Body mass indexif the patient gains weight rapidly

Consider

  • After each dose change
    • ECGif cardiovascular disease risk factors or disease

Hypothyroid patients

  • At 6 months
    • Thyroid function tests

Carbamazepine and thyroid hormones

Carbamazepine may reduce serum concentrations of thyroid hormones through enzyme induction. An increase in thyroid replacement may be required for patients with hypothyroidism.

Monitor thyroid function and adjust thyroid replacement therapy accordingly.

Ongoing once stable

Required

  • 6 monthly
    • Urea and electrolytesmore frequently if clinically indicated
  • Periodically
    • Liver function testsparticularly in patients with a history of liver disease and in elderly patients

Consider

  • Periodically
    • Plasma carbamazepine concentration

When to consider plasma carbamazepine concentrations

Routine monitoring of plasma carbamazepine concentrations is not recommended; however, levels may be useful where the patient:

  • Shows a change in clinical condition (loss of condition control)
  • Becomes pregnant
  • Has poor adherence
  • Has suspected toxicity
  • Is a child or adolescent

Abnormal results

Leucopenia

Treatment should be discontinued if leucopenia develops that is severe, progressive, or accompanied by clinical manifestations (e.g. fever or sore throat), or if any evidence of significant bone marrow suppression occurs.

Full blood count

An abnormal full blood count may warrant additional monitoring of serum iron levels.

Hepatic function

Withdraw treatment immediately in cases of aggravated liver dysfunction or acute liver disease.

Some liver function tests in patients receiving carbamazepine may be found to be abnormal, particularly gamma glutamyl transferase. This is probably due to hepatic enzyme induction. Enzyme induction may also produce modest elevations in alkaline phosphatase. These enhancements of hepatic metabolising capacity are not an indication for the withdrawal of carbamazepine.

Sodium

Hyponatraemia, particularly in patients taking diuretics should not deter treatment if the patient is asymptomatic (and sodium levels are above 120 mmol/L.

Notes

Advice to patients

Advise patients and carers to be aware of the signs of blood, liver, or skin disorders. They should seek immediate medical attention if symptoms develop such as:

  • Fever
  • Sore throat
  • Rash
  • Mouth ulcers
  • Bruising
  • Bleeding

Interpreting carbamazepine levels

The plasma carbamazepine concentration for optimum response 4–12 mg/litre (20–50 micromol/litre).

Bibliography