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Carbamazepine poisoning

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  • See also

    Poisoning – Acute guidelines for initial management 
    Resuscitation 
    Anticholinergic Syndrome

    Key Points

    1. Carbamazepine poisoning may have 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 the Poisons Information Centre 13 11 26

    Background

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

    Clinical features include:

    • drowsiness 
    • nausea and vomiting 
    • anticholinergic effects 
    • seizures
    • coma
    • life-threatening arrhythmias 

    Large carbamazepine ingestions can result in prolonged or delayed (>48 hours) symptoms due to slow and erratic absorption, secondary to anticholinergic effects causing ileus and ongoing absorption.

    Children requiring assessment

    • All children with deliberate self-poisoning or significant (>20 mg/kg OR >20 mg/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

    Red flag features in Red

    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
      • Ingestion of 50 mg/kg (or more than 3g) is associated with significant toxicity
    • Co-ingestants e.g. paracetamol

    Examination

    • CNS: ataxia, nystagmus, drowsiness, coma, seizures
    • Cardiovascular system: 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.)

    Investigations

    • ECG: initially and repeat at 6 hours until normal  
    • Paracetemol concentration in all intentional overdoses
    • Consider the possibility of other co-ingestants, either accidental or deliberate

    Carbamazepine concentration:

     mg/L  Micromol/L  Effect 
      5-12   20-50   Therapeutic range
      10-20   40-85   Nystagmus, sedation, ataxia
      20-40   85-170   Horizontal and vertical nystagmus, coma
      40 mg/L   >170   Respiratory depression, seizures, cardiac arrhythmia
       *Children are at risk of severe features at lower concentrations compared to adults  


    Acute Management

    Children Requiring Treatment

    • All symptomatic children
    • Acute ingestion of unknown quantity
    • Based on ingestion amount:
      • if child not usually on carbamazepine: dose >20 mg/kg
      • if child on regular carbamazepine: >20 mg/kg above the child's usual daily dose 

    1. Resuscitation

    • Supportive treatment to maintain adequate blood pressure and electrolyte balance is essential
    • IV fluid resuscitation 20 mL/kg for hypovolaemia or hypotension

    2. Decontamination 

    • This must be in discussion with a toxicologist 
      • Consider activated charcoal if massive ingestion (e.g. >50 mg/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 

    Ongoing care and monitoring

    Mild symptoms

    (e.g. ataxia, blurred vision)

    • Observe for a minimum of 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.

    Consider consultation with local paediatric team when 

    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 the Poisons Information Centre 13 11 26 for advice

    Consider transfer when 

    Children with severe symptoms with the potential to require intensive care review or care required is beyond the comfort level of the hospital

    For emergency advice and paediatric or neonatal ICU transfers, see Retrieval Services

    Consider discharge when

    • Normal GCS
    • Normal ECG
    • Child remains symptom free after 8 hour period of observation

    Assessing risk and connecting to community services

    • Prior to discharge, adolescents who present with deliberate ingestions need a risk assessment regarding the likelihood of further ingestions or other attempts to self-harm
    • Assessment of other drug and alcohol use should also be undertaken
    • If, after risk assessment, it is deemed safe to discharge a patient from hospital, but ongoing mental health or drug and alcohol needs are identified, the adolescent should be linked with appropriate services 

    Discharge information and follow-up

    Parent Information Sheet: Poisoning prevention for children

    Poisons Information Centre: phone 13 11 26

    Websites: 

    Mental Health, Drug and Alcohol Services


    New South Wales

    Child and Adolescent Mental Health Services: services delivered across NSW Health with referrals made via the NSW Mental Health Line (1800 011 511) for 24-hour advice, assessment referral information

    Youth Health and Wellbeing: includes links to Assessment Guideline for providers caring for young people aged 12 – 24 years across settings, as well as links to other resources 

    Your room: information on alcohol and other drug use, including fact sheets (multiple languages), assessment tools and links to support services 


    Queensland

    Child and Youth Mental Health Services: specialise in helping infants, children and young people up to age 18 years with complex mental health needs

    Dovetail: provides clinical advice and professional support to workers, services and communities who engage with young people affected by alcohol and other drug use

    Queensland Youth AOD Services Guide: created by Dovetail, this guide provides an overview of youth alcohol and other drug treatment services across Queensland. For help outside of hours, call the 24-hour Alcohol and Drug Information Service (ADIS) on 1800 177 833

    Clarence St, Mater Young Adult Health Service: Youth drug and alcohol service


    Victoria

    Child & Adolescent Mental Health Services (CAMHS): Victorian government mental health services are region-based

    YSAS (Youth Support and Advocacy Service): Outreach teams across Melbourne and regional Victoria for young people experiencing significant problems with alcohol and/or drug use

    YoDAA: Victoria’s Youth Drug and Alcohol Advice service - provides information and support for youth AOD needs or anyone concerned about a young person

    Infoxchange Service Seeker: Search for local community support services e.g. local doctor, dentist, counselling services, drug and alcohol services

    Last Updated July 2020

  • Reference List

    1. IBM Micromedex 2019, Carbamazepine. Retrieved from https://www.micromedexsolutions.com.acs.hcn.com.au/micromedex2/librarian/PFDefaultActionId/evidencexpert.DoIntegratedSearch?navitem=topHome&isToolPage=true# (viewed November 2019)
    2. National Poisons Centre New Zealand 2019, Carbamazepine. Retrieved from TOXINZ™ Poisons Information, https://www.toxinz.com.acs.hcn.com.au/Spec/1873230 (viewed November 2019)