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 allele if Han Chinese or Thai origin patient
- ECG if 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 concentration take blood immediately before next dose (trough level)
- At 6 months
- Full blood count
- Urea and electrolytes
- Liver function tests
- Body mass index if the patient gains weight rapidly
Consider
- After each dose change
- ECG if 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 electrolytes more frequently if clinically indicated
- Periodically
- Liver function tests particularly 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
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