Poisoning - Antihistamines in Children

Pediatric emergencies

Clinicals - History

Fact Explanation
Drowsiness, fatigue, impairment of memory, somnolence Due to central nervous system (CNS) toxicity. Antihistamine causes interference with neurotransmitter effect of histamine through H1 receptor and causes CNS depression Drowsiness, fatigue, impairment of memory, somnolence
Due to central nervous system (CNS) toxicity. Antihistamine causes interference with neurotransmitter effect of histamine through H1 receptor and causes CNS depression
Convulsions, confusion, agitation, a sensory experience of something that does not exist outside (hallucination) Infants and children often exhibit initial paradoxical CNS stimulation, including agitation, hallucinations, confusion and convulsions before progressing to coma Convulsions, confusion, agitation, a sensory experience of something that does not exist outside (hallucination)
Infants and children often exhibit initial paradoxical CNS stimulation, including agitation, hallucinations, confusion and convulsions before progressing to coma
Palpitations Due to cardiac toxicity.
Antihistamine overdose can produce a variety of cardiac arrhythmias. For the majority of antihistamines this effect is mediated by myocardial sodium channel blockade—a quinidine like effect. Two of the newer non-sedating antihistamines, terfenadine and astemizole, cause delayed cardiac repolarization by potassium channel blockade. This is associated with prolongation of the QT interval and may predispose to the development of ventricular tachyarrhythmias
Palpitations
Due to cardiac toxicity.
Antihistamine overdose can produce a variety of cardiac arrhythmias. For the majority of antihistamines this effect is mediated by myocardial sodium channel blockade—a quinidine like effect. Two of the newer non-sedating antihistamines, terfenadine and astemizole, cause delayed cardiac repolarization by potassium channel blockade. This is associated with prolongation of the QT interval and may predispose to the development of ventricular tachyarrhythmias
Dry eyes , dry mouth, urinary retention, constipation, erectile dysfunction Due to anticholinergic effects of anti histamine toxicity Dry eyes , dry mouth, urinary retention, constipation, erectile dysfunction
Due to anticholinergic effects of anti histamine toxicity
Nausea, vomiting Due to anticholinergic effects of anti histamine toxicity Nausea, vomiting
Due to anticholinergic effects of anti histamine toxicity
Fever Hyperthermia may occur due to impaired sweating (anticholinergic effect), increased production of heat (excessive motor activity, agitation and seizures) and central effects on thermoregulation Fever
Hyperthermia may occur due to impaired sweating (anticholinergic effect), increased production of heat (excessive motor activity, agitation and seizures) and central effects on thermoregulation
Poor socio economic status Toxicity due to over dose is high due to poor parental education, poor supervision of the parents Poor socio economic status
Toxicity due to over dose is high due to poor parental education, poor supervision of the parents

Clinicals - Examination

Fact Explanation
Drowsiness Due to central nervous system (CNS) toxicity. Antihistamine causes interference with neurotransmitter effect of histamine through H1 receptor and causes CNS depression.It can cause coma in severe toxicity Drowsiness
Due to central nervous system (CNS) toxicity. Antihistamine causes interference with neurotransmitter effect of histamine through H1 receptor and causes CNS depression.It can cause coma in severe toxicity
Agitation, seizures Infants and children often exhibit initial paradoxical CNS stimulation, including agitation, hallucinations, confusion and convulsions before progressing to coma Agitation, seizures
Infants and children often exhibit initial paradoxical CNS stimulation, including agitation, hallucinations, confusion and convulsions before progressing to coma
Tachycardia Due to cardiovascular system toxicity.Antihistamine overdose can produce a variety of cardiac arrhythmias. For the majority of antihistamines this effect is mediated by myocardial sodium channel blockade—a quinidine like effect. Two of the newer non-sedating antihistamines, terfenadine and astemizole, cause delayed cardiac repolarization by potassium channel blockade. This is associated with prolongation of the QT interval and may predispose to the development of ventricular tachyarrhythmias Tachycardia
Due to cardiovascular system toxicity.Antihistamine overdose can produce a variety of cardiac arrhythmias. For the majority of antihistamines this effect is mediated by myocardial sodium channel blockade—a quinidine like effect. Two of the newer non-sedating antihistamines, terfenadine and astemizole, cause delayed cardiac repolarization by potassium channel blockade. This is associated with prolongation of the QT interval and may predispose to the development of ventricular tachyarrhythmias
Dry eyes, dry mouth, pupillary dilatation Due to anticholinergic effects of anti histamine toxicity Dry eyes, dry mouth, pupillary dilatation
Due to anticholinergic effects of anti histamine toxicity
Hypotension Relative volume depletion and vasodilatation resulting from alpha receptor blockade Hypotension
Relative volume depletion and vasodilatation resulting from alpha receptor blockade
Febrile Hyperthermia may occur due to impaired sweating (anticholinergic effect), increased production of heat (excessive motor activity, agitation and seizures) and central effects on thermoregulation Febrile
Hyperthermia may occur due to impaired sweating (anticholinergic effect), increased production of heat (excessive motor activity, agitation and seizures) and central effects on thermoregulation

Investigations - Diagnosis

Fact Explanation
Electrocardiogram To identify arrhythmia.
Antihistamine overdose can produce a variety of cardiac arrhythmias. For the majority of antihistamines this effect is mediated by myocardial sodium channel blockade—a quinidine like effect. Two of the newer non-sedating antihistamines, terfenadine and astemizole, cause delayed cardiac repolarization by potassium channel blockade. This is associated with prolongation of the QT interval and may predispose to the development of ventricular tachyarrhythmias
Electrocardiogram
To identify arrhythmia.
Antihistamine overdose can produce a variety of cardiac arrhythmias. For the majority of antihistamines this effect is mediated by myocardial sodium channel blockade—a quinidine like effect. Two of the newer non-sedating antihistamines, terfenadine and astemizole, cause delayed cardiac repolarization by potassium channel blockade. This is associated with prolongation of the QT interval and may predispose to the development of ventricular tachyarrhythmias
Full blood count Uncommonly, agranulocytosis has been reported with chlorpheniramine and brompheniramine Full blood count
Uncommonly, agranulocytosis has been reported with chlorpheniramine and brompheniramine

Investigations - Management

Fact Explanation
Electrocardiogram Patients with QT prolongation should be monitored until these changes resolve Electrocardiogram
Patients with QT prolongation should be monitored until these changes resolve
Arterial blood gas analysis All unconscious patients require arterial blood gas to access adequacy of ventilation and to ensure they are not acidotic Arterial blood gas analysis
All unconscious patients require arterial blood gas to access adequacy of ventilation and to ensure they are not acidotic
Electrocardiogram This may be helpful in excluding other differentials (eg : normal ECG in central nervous system infections) Electrocardiogram
This may be helpful in excluding other differentials (eg : normal ECG in central nervous system infections)
Full blood count To exclude central nervous system infections and other systemic infections which may present with drowsiness.Infections will show leukocytosis in full blood count Full blood count
To exclude central nervous system infections and other systemic infections which may present with drowsiness.Infections will show leukocytosis in full blood count
creatine kinase level This may be helpful if suspecting rhabdomyolysis secondary to antihistamine/decongestant combination which contains pseudoephedrine or phenylephrine creatine kinase level
This may be helpful if suspecting rhabdomyolysis secondary to antihistamine/decongestant combination which contains pseudoephedrine or phenylephrine

Management - Supportive

Fact Explanation
General emergency management - air way , breathing, circulation All patients should have assessment of the adequacy of their airway protection and ventilation. Intravenous fluid may be required to maintain the circulation General emergency management - air way , breathing, circulation
All patients should have assessment of the adequacy of their airway protection and ventilation. Intravenous fluid may be required to maintain the circulation
Parental education , Community based programs Parents should teach young children about the dangers of medicines. Advise the parents about the proper storage and labeling of medicines. Inform parents about common medications that may be dangerous. Educate parents that they need to supervise their children Parental education , Community based programs
Parents should teach young children about the dangers of medicines. Advise the parents about the proper storage and labeling of medicines. Inform parents about common medications that may be dangerous. Educate parents that they need to supervise their children

Management - Specific

Fact Explanation
Gastrointestinal decontamination Activated charcoal should be considered up to four hours post-ingestion Gastrointestinal decontamination
Activated charcoal should be considered up to four hours post-ingestion
Intra venous fluid For the treatment of hypotension Intra venous fluid
For the treatment of hypotension
Benzodiazepine ( Diazepam ) Convulsions and paradoxical excitement can be treated with a benzodiazepine Benzodiazepine ( Diazepam )
Convulsions and paradoxical excitement can be treated with a benzodiazepine
Sodium bicarbonate Sodium bicarbonate is the first drug of choice for QT prolongation with sodium channel blocking antihistamines Sodium bicarbonate
Sodium bicarbonate is the first drug of choice for QT prolongation with sodium channel blocking antihistamines

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