≪ View Page

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Next revision		Previous revision
wikitox:2.1.11.4.2_antihistamines [2025/06/02 22:32] – kharriswikitox:2.1.11.4.2_antihistamines [2025/06/03 00:08] (current) – kharris
Line 3: Line 3:
 ---- ----
  
-===== SUMMARY =====+===== OVERVIEW =====
  
-This monograph discusses the assessment and management of sedating antihistamines. For management of less-sedating antihistamines, see [[:wikitox:2.1.11.4.2_antihistamines:wikitox:non_sedating_antihistamines|Non-Sedating Anithistamines]]+This monograph discusses the assessment and management of sedating antihistamines. For management of less-sedating antihistamines, see [[:wikitox:non_sedating_antihistamines|Non-Sedating Antihistamines]]
  
 There are many agents in this class including brompheniramine, chlorphenamine, cyclizine, cyproheptadine, dexchlorpheniramine, dimenhydrinate, diphenhydramine, doxylamine, pheniramine and promethazine. Many are available as individual agents, but several can also be found in co-formulation with other medications such as ibuprofen and paracetamol in cold and flu medicines or motion sickness remedies. There are many agents in this class including brompheniramine, chlorphenamine, cyclizine, cyproheptadine, dexchlorpheniramine, dimenhydrinate, diphenhydramine, doxylamine, pheniramine and promethazine. Many are available as individual agents, but several can also be found in co-formulation with other medications such as ibuprofen and paracetamol in cold and flu medicines or motion sickness remedies.
Line 21: Line 21:
 ===== RISK ASSESSMENT ===== ===== RISK ASSESSMENT =====
  
-With the exception of diphenhydramine, dimenhydrinate and promethazine, the toxic dose of agents is not well defined, except to say that toxicity is dose dependant.+With the exception of diphenhydramine, dimenhydrinate and promethazine, the toxic dose of agents is not well defined, except to say that toxicity is dose dependent.
  
 **Diphenhydramine**: Ingestions of >1g are associated with severe effects. Ingestion of <300mg or (<7.5mg/kg in children) are unlikely to have significant effects. **Diphenhydramine**: Ingestions of >1g are associated with severe effects. Ingestion of <300mg or (<7.5mg/kg in children) are unlikely to have significant effects.
Line 34: Line 34:
 Sedating antihistamines are generally well absorbed from the gastrointestinal tract, with peak plasma concentrations typically reached within 2 to 3 hours after oral administration. Sedating antihistamines are generally well absorbed from the gastrointestinal tract, with peak plasma concentrations typically reached within 2 to 3 hours after oral administration.
  
-==== Distrubution ====+==== Distribution ====
  
 These drugs are lipophilic and widely distributed throughout the body, readily crossing the blood–brain barrier, which contributes to their central sedative effects. These drugs are lipophilic and widely distributed throughout the body, readily crossing the blood–brain barrier, which contributes to their central sedative effects.
Line 48: Line 48:
 ===== CLINICAL EFFECTS ===== ===== CLINICAL EFFECTS =====
  
-In general ingestions of all agents in this group lead to dose-dependant sedation and anticholinergic toxicity. The initial sedation often masks an underlying anticholinergic delirium which then becomes more troublesome as the sedation lifts (typically after 6-18hrs).+In general, ingestions of all agents in this group lead to dose-dependent sedation and anticholinergic toxicity. The initial sedation often masks an underlying anticholinergic delirium which then becomes more troublesome as the sedation lifts (typically after 6-18hrs).
  
   * **CNS**: sedation (dose-dependent), anticholinergic toxicity, seizures (most commonly seen with pheniramine).   * **CNS**: sedation (dose-dependent), anticholinergic toxicity, seizures (most commonly seen with pheniramine).
Line 59: Line 59:
   * **Creatine kinase**: Detect rhabdomyolysis in cases of doxylamine or diphenhydramine toxicity.   * **Creatine kinase**: Detect rhabdomyolysis in cases of doxylamine or diphenhydramine toxicity.
 ===== TREATMENT ===== ===== TREATMENT =====
- 
----- 
  
 ==== Supportive ==== ==== Supportive ====
Line 76: Line 74:
 Hypotension can occur and is commonly related to alpha blockade induced vasodilation and responds to IV hydration. Hypotension can occur and is commonly related to alpha blockade induced vasodilation and responds to IV hydration.
  
-If there is evidence of QRS widening or QT-interval prolongation on ECG, then the patient should remain on continuous cardiac monitoring. Manage urgently according to advice on ECG in toxicology ECG [WikiTox]+If there is evidence of QRS widening or QT-interval prolongation on ECG, then the patient should remain on continuous cardiac monitoring. Manage urgently according to advice on [[:concept_ecg_changes|ECG in Toxicology]]
  
 ==== Decontamination ==== ==== Decontamination ====
Line 100: Line 98:
 ===== REFERENCES ===== ===== REFERENCES =====
  
-  - Buckley NA, Whyte IM, Dawson AH, Cruickshank DA. Pheniramine–a much abused drug. Med J Aust. 1994 Feb 21;160(4):188-92. PMID: 7906008. PDF +  - Buckley NA, Whyte IM, Dawson AH, Cruickshank DA. Pheniramine–a much abused drug. Med J Aust. 1994 Feb 21;160(4):188-92. PMID: 7906008. {{:wikitox:buckley_-_pheniramine_a_much_abused_drug.pdf|PDF}} 
-  - Page CB, Duffull SB, Whyte IM, Isbister GK. Promethazine overdose: clinical effects, predicting delirium and the effect of charcoal. QJM. 2009 Feb;102(2):123-31. doi: 10.1093/qjmed/hcn153. Epub 2008 Nov 28. PMID: 19042969. PDF +  - Page CB, Duffull SB, Whyte IM, Isbister GK. Promethazine overdose: clinical effects, predicting delirium and the effect of charcoal. QJM. 2009 Feb;102(2):123-31. doi: 10.1093/qjmed/hcn153. Epub 2008 Nov 28. PMID: 19042969. {{:wikitox:page_-_promethazine_overdose_delirium.pdf|PDF}} 
-  - Poluzzi E, Raschi E, Godman B, Koci A, Moretti U, Kalaba M, Wettermark B, Sturkenboom M, De Ponti F. Pro-arrhythmic potential of oral antihistamines (H1): combining adverse event reports with drug utilization data across Europe. PLoS One. 2015 Mar 18;10(3):e0119551. doi: 10.1371/journal.pone.0119551. PMID: 25785934; PMCID: PMC4364720. PDF +  - Poluzzi E, Raschi E, Godman B, Koci A, Moretti U, Kalaba M, Wettermark B, Sturkenboom M, De Ponti F. Pro-arrhythmic potential of oral antihistamines (H1): combining adverse event reports with drug utilization data across Europe. PLoS One. 2015 Mar 18;10(3):e0119551. doi: 10.1371/journal.pone.0119551. PMID: 25785934; PMCID: PMC4364720. {{:wikitox:pro-arrhythmic_potential_of_or.pdf|PDF}} 
-  - Scharman EJ, Erdman AR, Wax PM, Chyka PA, Caravati EM, Nelson LS, Manoguerra AS, Christianson G, Olson KR, Woolf AD, Keyes DC, Booze LL, Troutman WG. Diphenhydramine and dimenhydrinate poisoning: an evidence-based consensus guideline for out-of-hospital management. Clin Toxicol (Phila). 2006;44(3):205-23. doi: 10.1080/15563650600585920. PMID: 16749537. PDF +  - Scharman EJ, Erdman AR, Wax PM, Chyka PA, Caravati EM, Nelson LS, Manoguerra AS, Christianson G, Olson KR, Woolf AD, Keyes DC, Booze LL, Troutman WG. Diphenhydramine and dimenhydrinate poisoning: an evidence-based consensus guideline for out-of-hospital management. Clin Toxicol (Phila). 2006;44(3):205-23. doi: 10.1080/15563650600585920. PMID: 16749537. {{:wikitox:diphenhydramine_and_dimenhydrinate_poisoning_an_evidence-based_consensus_guideline_for_out-of-hospital_management.pdf|PDF}} 
-  - Köppel C, Tenczer J, Ibe K. Poisoning with over-the-counter doxylamine preparations: an evaluation of 109 cases. Hum Toxicol. 1987 Sep;6(5):355-9. doi: 10.1177/096032718700600503. PMID: 3679242. PDF +  - Köppel C, Tenczer J, Ibe K. Poisoning with over-the-counter doxylamine preparations: an evaluation of 109 cases. Hum Toxicol. 1987 Sep;6(5):355-9. doi: 10.1177/096032718700600503. PMID: 3679242. {{:wikitox:koppel-et-al-1987-poisoning-with-over-the-counter-doxylamine-preparations-an-evaluation-of-109-cases.pdf|PDF}} 
-  - Köppel C, Ibe K, Tenczer J. Clinical symptomatology of diphenhydramine overdose: an evaluation of 136 cases in 1982 to 1985. J Toxicol Clin Toxicol. 1987;25(1-2):53-70. doi: 10.3109/15563658708992613. PMID: 3586086. PDF+  - Köppel C, Ibe K, Tenczer J. Clinical symptomatology of diphenhydramine overdose: an evaluation of 136 cases in 1982 to 1985. J Toxicol Clin Toxicol. 1987;25(1-2):53-70. doi: 10.3109/15563658708992613. PMID: 3586086. {{:wikitox:clinical_symptomatology_of_diphenhydramine_overdose_an_evaluation_of_136_cases_in_1982_to_1985.pdf|PDF}}