Carbamazepine poisoning


  • Statewide logo

    This guideline has been adapted for statewide use with the support of the Victorian Paediatric Clinical Network

  • See also

    Poisoning – Acute guidelines for initial management 
    Resuscitation 
    Anticholinergic Syndrome

    Key Points

    1. Carbamazepine poisoning may result in prolonged or delayed onset of symptoms, and children require observation for development of clinical manifestations.
    2. There is reasonable correlation between carbamazepine serum concentrations and clinical effects, and concentrations can be particularly helpful in large ingestions.
    3. Decontamination should be considered for children with large ingestions in consultation with a toxicologist.

    For 24 hour advice, contact Victorian Poisons Information Centre 131126

    Background

    Clinical features of toxicity generally develop within 1-2 hours for immediate release preparations and 4-8 hours in sustained release. Symptoms are dose-dependent and monitoring drug concentrations can be helpful.

    Clinical features include drowsiness, nausea and vomiting, anticholinergic effects, seizures, coma and life-threatening arrhythmias. Large carbamazepine ingestions can result in prolonged or delayed (>48hours) symptoms due to slow and erratic absorption due to the anticholinergic effects causing ileus and on-going absorption.

    Children requiring assessment

    All children with deliberate self-poisoning or significant (>20mg/kg OR >20mg/kg greater than the child’s usual daily dose if on a regular dose) accidental ingestion.      
    Any symptomatic child.      
    Acute ingestion of unknown quantity.     
    Any child where the developmental age is inconsistent with accidental poisoning as non-accidental poisoning should be considered.

    Risk Assessment

    History:

    Intentional overdose or accidental
    Dose:
    Stated or likely dose taken
    Presented as syrup, immediate or modified-release tablets
    If possible determine the exact name and tablet size.
    Calculate the maximum possible dose per kg

    Co-ingestants e.g. paracetamol

    Examination:

    • CNS
      • Ataxia, nystagmus, drowsiness, coma, seizures
    • CVS
      • Tachycardia, hypotension, life threatening arrhythmias (heart block, widening of QRS, ventricular fibrillation)
    • Anticholinergic effects
      • Urinary retention, decreased bowel motility, dry mouth and sinus tachycardia

    Always check for Medicalert bracelet in any unconscious patient, or any other signs of underlying medical condition (fingerprick marks etc.)

    Consider the possibility of co ingestions, either accidental or deliberate

    Investigations:

    ECG: (initially and repeat at 6 hours until normal).  

    Carbamazepine concentration

    Toxic concentration

    • 20 to 50 micromol/L (5 to 12 mg/L) — therapeutic range
    • 40 to 85 micromol/L (10 to 20 mg/L) — nystagmus, sedation, ataxia
    • 85 to 170 micromol/L (20 to 40 mg/L) — horizontal and vertical nystagmus, coma
    • >170 micromol/L (40 mg/L) — respiratory depression, seizures, cardiac arrhythmia (Compared with adults, children can be at risk of severe features at lower concentrations)

    Dose-response relationship

    • Ingestion of 50mg/kg (or more than 3g) is associated with significant toxicity

    Paracetamol concentration in all intentional overdoses

    Acute Management

    Children Requiring Treatment

    • All symptomatic children
    • Acute ingestion of unknown quantity
    • Based on ingestion amount:
      • Carbamazepine ingestion of >20mg/kg OR the greater of more than twice the daily dose or >20mg/kg if the child is on maintenance carbamazepine treatment

    Resuscitation

    • Standard procedures and supportive care

    Decontamination 

    • This must be in discussion with a toxicologist –  contact the Poisons Information Centre on 13 11 26
    • Consider activated charcoal if massive ingestion (e.g. >50mg/kg) and within 24 hours, or after large ingestion of controlled release preparations. (In setting of CNS toxicity, activated charcoal should only be administered once airway protection is secured).
    • Multidose activated charcoal may be indicated in children with large ingestions, provided bowel sounds are present. Discuss with a toxicologist.

    Mild symptoms (e.g. ataxia, blurred vision)

    • Observe minimum  8 hours post-ingestion and consider longer if controlled-release formulation
    • Discharge once symptom-free

    Moderate-to-severe or persistent symptoms after 8 hours of observation (e.g. Depressed conscious state or cardiac arrhythmias)

    • Admit for observation and supportive management
    • Discussion with toxicologist regarding monitoring of drug concentration monitoring
    • Discussion with paediatric intensive care team if severe symptoms

    Management of seizures

    • Benzodiazepines should be used to terminate seizures that are not self-resolving. Sodium channel blocking anticonvulsants (e.g. phenytoin) are relatively contraindicated.

    When to admit/consult local paediatric team, or who/when to phone 

    Admission should be considered for all children and young people with an intentional overdose or in children with persisting symptoms after 8 hours observation

    Consult Contact Victorian Poisons Information Centre 131126 for advice

    When to consider transfer to a tertiary centre 

    Children with severe symptoms with the potential to require intensive care review

    For emergency advice and paediatric or neonatal ICU transfers, call the Paediatric Infant Perinatal Emergency Retrieval (PIPER) Service: 1300 137 650.

    Discharge Criteria 

    Normal GCS
    Normal ECG
    Period of observation as above
    For deliberate ingestion a risk assessment should indicate that the child is at low risk of further self-harm in the discharge setting

    Discharge information and follow-up

    Poisoning prevention for children Parent information

    Victorian Poisons Information Centre: 13 11 26 www.austin.org.au/poisons

    Intentional self –harm: Referral to local mental health services e.g. Orygen Youth Health: 1800 888 320 

    Recreational poisoning: Referral to YoDAA, Victoria's Youth Drug and Alcohol Advice service: 1800 458 685

     

    Last Updated December 2017