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Medicines Monitoring

Carbamazepine monitoring

Published Last updated
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
  3. After started or dose changed
    1. Required
    2. Consider
    3. Hypothyroid patients
  5. Ongoing once stable
    1. Required
    2. Consider
    3. Interpreting carbamazepine levels
  7. Abnormal results
    1. Leucopenia
    2. Full blood count
    3. Hepatic function
    4. Sodium
    5. Vitamin D
  9. Notes
    1. Advice to patients
    2. Brand prescribing
    3. Bone fracture
  11. Bibliography
  12. Update history

Before starting

Required

  • Baseline
    • Body mass index or Body weight
    • Full blood count
    • Liver function tests
    • Urea and electrolytes
    • Serum sodium
    • HLAB* 1502 alleleif Han Chinese or Thai origin patient

Han Chinese, Thai or other Asian patients

Screen for HLA-B*1502 allele genotype for individuals with Han Chinese, or Thai ancestry. These patients may be at increased risk of Stevens-Johnson syndrome when treated with carbamazepine. Consider screening for other at-risk Asian populations such as Philippines, Malaysia and Vietnam.

Consider

  • Baseline
    • Serum creatinine (for creatinine clearance) or Estimated glomerular filtration rate
    • Reticulocytes
    • Serum iron
    • ECGif cardiovascular disease risk factors or disease
    • Vitamin D

After started or dose changed

Required

  • After 2 weeks then monthly for 3 months
    • Serum sodiumif patient has pre-existing renal impairment or is taking a sodium-lowering medicine, such as a diuretic, ongoing monitoring according to clinical need.

Consider

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

Hypothyroid patients

  • Within 2 to 3 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

  • Periodically
    • Urea and electrolytes
    • Liver function testsparticularly in patients with a history of liver disease and in elderly patients
    • Vitamin D

Consider

  • Periodically
    • Plasma carbamazepine concentration

Routine monitoring of plasma carbamazepine concentrations is not recommended. Consider monitoring when investigating:

  • adherence
  • unexplained loss of seizure control
  • suspected toxicity
  • pharmacokinetic interaction
  • onset of specific clinical condition, such as pregnancy, organ failure or status epilepticus

Interpreting carbamazepine levels

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

Abnormal results

Leucopenia

Treatment should be discontinued if leucopenia develops that is severe, progressive, or accompanied by clinical manifestations, such as 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

  • Asymptomatic mild hyponatraemia (sodium levels above 120 mmol/L) treatment can continue.
  • Review carbamazepine treatment and correct sodium as clinically appropriate for patients with symptoms or a sodium level less than 120 mmol/L.

Hyponatraemia can occur with carbamazepine, particularly in patients with pre-existing renal impairment or taking diuretics.

Vitamin D

Carbamazepine is thought to affect bone mineral metabolism which may lead to vitamin D deficiency, hypocalcaemia, and hypophosphatemia in chronically treated patients with epilepsy. Consider vitamin D supplementation.

Notes

Advice to patients

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

  • fever
  • sore throat
  • rash
  • mouth ulcers
  • bruising
  • bleeding

Advise patients and carers to be aware of the signs of suicidal ideation and behaviours. Seek immediate medical attention if symptoms develop such as:

  • mood changes
  • distressing or suicidal thoughts

Brand prescribing

Carbamazepine is classified by the MHRA as a category 1 medicine. People treated for epilepsy should be maintained on a specific manufacturer’s preparation of carbamazepine.

Bone fracture

Decreasing bone mineral density, osteopenia, osteoporosis and fractures may occur in patients on long term-therapy with carbamazepine. Consider vitamin D supplementation for people with risk factors for these conditions who are on long-term carbamazepine. Risk factors include:

  • immobility for long periods
  • inadequate sun exposure
  • inadequate dietary calcium intake

Bibliography

Update history

  1. Full review and update. HLAB* 1502 allele moved to required from consider if Han Chinese or Thai origin at baseline. Additional information added to abnormal results section for Vitamin D and bone fracture.
  1. Published