In this section
Poisoning – acute guidelines for initial managementResuscitation Anticholinergic Poisoning
For 24 hour advice, contact the Victorian Poisons Information Centre on 13 11 26
Antihistamines are commonly recommended for the treatment of allergic symptoms. This guideline will only deal with H1 antagonists. H2 antagonists such as cimetidine and ranitidine are not covered by this guideline.
Antihistamines are divided into sedating and lesser sedating (previous called non-sedating) types. In general, the lesser sedating antihistamines have less serious toxicity in overdose.
As well as their H1 effect, sedating antihistamines can have alpha adrenergic, anticholinergic and serotonergic effects. As well as sedation, overdose often presents with anticholinergic symptoms (see Anticholinergic Poisoning). At higher doses, they can also cause sodium channel blockade with subsequent cardiovascular effects including QT prolongations and Torsades de Pointes.
Lesser sedating antihistamines
These medicines cause mostly peripheral H1 blockade with limited penetration into the CNS. In overdose symptoms can include dizziness, tachycardia, headache drowsiness or agitation. While the current generation of lesser sedating antihistamines do not affect the QT interval at normal doses (unlike the previous generation of medicines), there are concerns there may be some effect in overdose.
All children or young people with intentional self-poisoning or significant accidental ingestion
Any symptomatic child or young person
Any child whose developmental age is inconsistent with accidental poisoning as non-accidental poisoning should be considered.
Intentional poisoning or accidental
Co-ingestants e.g. paracetamol
See Anticholinergic Poisoning
For those requiring further assessment:
Standard procedures and supportive care
Admission should be considered for all children or young people with an intentional poisoning.
Consult Contact Victorian Poisons Information Centre 131126 for advice
Consider transfer when:
For emergency advice and paediatric or neonatal ICU transfers, call the Paediatric Infant Perinatal Emergency Retrieval (PIPER) Service: 1300 137 650.
If features of poisoning have not developed at 6 hours post-ingestion
For intentional poisoning, a risk assessment should indicate that the child or young person is at low risk of further self harm in the discharge setting
Accidental ingestion: Parent information sheet from Victorian Poisons Information centre on the prevention of poisoning:
Intentional self –harm: Referral to local mental health services e.g. Orygen Youth Health: 1800 888 320
Last updated August 2017