Carbamazepine | Epilepsy clinician handbook
- A first-line choice for focal seizures with or without progression to bilateral convulsive seizures, and childhood epilepsy with centro temporal spikes.
- Carbamazepine may worsen seizures in the primary generalised epilepsies such as CAE and JME.
Possible side effects
Incoordination (e.g. gait unsteadiness) or drowsiness can occur when a patient first starts carbamazepine. These are usually transient side effects (unsteadiness resolves over days to a couple of weeks) and the dose can continue to be increased gradually. Commencing slowly lessens these side effects.
Rashes, in particular Steven-Johnsons Syndrome (SJS), is the most important adverse effect to watch for.
- Rash most commonly occurs within 4-6 weeks but can occur at any time.
- Development of rash on carbamazepine warrants an immediate medical review.
- Particularly concerning signs to look out for are red eyes, mucosal involvement, and blistering.
- Suspected SJS requires appropriate (usually inpatient) medical management.
- Research has shown an increased risk of SJS in people of Han Chinese ethnicity with the HLA-B1502 allele. Care should be taken when considering carbamazepine in this population and HLA-B1502 testing is recommended before starting the drug in particular ethnic populations (Han Chinese, Filipinos, Malaysians, South Asians Indians, and Thai).
- The HLA testing in New South Wales can be done via a blood test using the Immunogenetics Request Form.
Other notable side effects:
- Neutropenia
- Transaminitis. Mild nonprogressive transaminitis does not necessarily require drug cessation.
- Syndrome of Inappropriate Antidiuretic Hormone secretion (SIADH).
- All anti-seizure medications are potentially teratogenic and this is often dose related.
- For a complete list of adverse effects, appropriate formularies should be consulted.
Interactions and precautions
- Tegretol is an enzyme inducer and therefore can lower valproate and phenytoin levels.
- It will also reduce the efficacy of the oral contraceptive pill.
- Avoid macrolides – particularly erythromycin – as it can alter carbamazepine levels and cause toxicity, including hyponatremia.
- Research has shown an increased risk of SJS in people of Han Chinese ethnicity with the HLA-B1502 allele. Care should be taken when considering carbamazepine in this population and HLA-B1502 testing is recommended before starting the drug in particular ethnic populations (Han Chinese, Filipinos, Malaysians, South Asians Indians, and Thai).
The HLA testing in New South Wales can be done via a blood test using the Immunogenetics Request Form.