Risperidone Poisoning

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    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
    Anticholinergic Syndrome

    Key points 

    1. Risperidone is an atypical antipsychotic agent associated with tachycardia and acute dystonic reactions
    2. Serious effects include cardiac instability such as arrhythmias and neurological instability including CNS depression, seizures and extra pyramidal symptoms
    3. Management is mainly supportive and symptomatic

    For 24 hour advice, contact the Poisons Information Centre 13 11 26


    Risperidone is an atypical antipsychotic that is a selective monoaminergic antagonist with strong affinity for serotonin type 2 (5-HT2) receptors and slightly weaker affinity for dopamine type 2 (D2) receptors.

    Risperidone blocks dopamine receptors resulting in extrapyramidal symptoms. Alpha-1 adrenergic effects are responsible for orthostatic hypotension. Its affinity, albeit low, for histamine receptors contributes to anticholinergic effects.


    • Symptoms generally develop within 1–2 hours and peak by 4–6 hours post ingestion
    • Delays in symptom onset have been reported, however (presumably for patients who are slow metabolisers)
    • Resolution of symptoms may take several days (half-life can vary depending on an individual’s metabolism, from 3–30 hours) 

    Children requiring assessment

    • Any symptomatic patient
    • Acute ingestion of unknown quantity
    • All children with deliberate self-poisoning or significant accidental ingestion  
    • Urgent assessment is required for all children who may have ingested the following: 
      • In drug naive children: 
        • less than 12 years of age, an ingestion of 1 mg should be considered potentially toxic
        • 12 years or older, an ingestion of more than 5 mg should be considered potentially toxic 
      • In children who take risperidone on a regular basis, a dose more than 5 times their current single dose (not daily dose) should be considered potentially toxic
    • Any child whose developmental age is inconsistent with accidental poisoning as non-accidental poisoning should be considered

    Risk assessment


    • Intentional overdose or accidental or therapeutic error 
    • Amount ingested 
    • Time of ingestion 
    • Co-ingestants eg alcohol and cannabis may enhance CNS depressant effect


    Toxicity usually manifests within 4 hours 

    Mild to moderate toxicity:

    • Cardiac: Tachycardia and hypotension are common
    • CNS: Depressed mental status, somnolence and extrapyramidal symptoms 

    Severe toxicity: 

    • Cardiac: QTc prolongation, ventricular arrhythmia
    • CNS: extrapyramidal symptoms likely
    • Respiratory depression, seizure, or coma could potentially occur, as well as neuroleptic malignant syndrome

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


    • Screening: 12 lead ECG, BSL, paracetamol level 
    • Specific:
        • ECG at presentation and 4 hours (onset of tachycardia can be delayed up to 20 hours)
        • Sinus tachycardia is common
        • QT prolongation (rare)

    Acute Management

    1. Resuscitation

    • Standard procedures and supportive care. See also Poisoning – acute guidelines for initial management
    • Treat hypotension with intravenous fluids. If hypotension persists administer vasopressor - norepinephrine is preferred. The manufacturer recommends avoidance of epinephrine and dopamine since beta stimulation may worsen hypotension in the setting of risperidone-induced alpha blockade

    2. Decontamination  

    • Activated charcoal has a very limited role in treatment. Discuss with a toxicologist via the Poisons Information Centre 13 11 26.

    3. Specific treatment

    • Seizure: administer IV benzodiazepines; add propofol or barbiturates if seizures recur or persist (avoid phenytoin or fosphenytoin). See Afebrile seizures   
    • Extrapyramidal symptoms: may occur up to several days post exposure 
      Treatment: Benzatropine 
      3–12  years, give 0.02 mg/kg IM or IV (maximum 1 mg)
      12–18 years, give 1–2 mg IM or IV  
      May need to repeat dosing in 15 minutes
      Avoid discharging patients requiring ongoing doses of benzatropine 

    Consider consultation with local paediatric team when

    Admission should be considered for

    • all children and adolescents with an intentional overdose
    • symptomatic patients
    • those with an overdose in the presence of cardiovascular or neurological disease
    Consult Victorian Poisons Information Centre 13 11 26 for advice

    Consider transfer when

    • There is significant CNS depression/seizures or any cardiovascular instability
    • Children requiring care beyond the comfort level of the current hospital  

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

    Consider discharge when

    • Normal GCS
    • Normal ECG 
    • Period of observation  
    • Warn that extrapyramidal movements may occur up to 3 days later

    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 (see links below for services in the State of Victoria)  

    Discharge information and follow-up:

    Parent Information: Poisoning prevention for children 

    Prevention of poisoning (Victorian Poisons Information Centre) 

    Poisons Information Centre: phone 13 11 26


    Poisons Information Centre

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

    Orygen Youth Health: Specialist mental health services for people aged 15–25 years, residing in the western and north-western regions of metropolitan Melbourne. Triage/intake - 1800 888 320.

    Headspace: National Youth Mental Health Foundation with local headspace centres

    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 September 2020