Promethazine

ALLERGY AND ANAPHYLAXIS — Antihistamines — Sedating antihistamines

AMH 2022 section 1.2.1

Active ingredients (generic names)	PROMETHAZINE (pro-meth-a-zeen) Other sedating antihistamines Not included in this monograph — see AMH for information: Alimemazine Cyclizine Cyproheptadine Dexchlorpheniramine Diphenhydramine Doxylamine MB-PROMETHAZINE.pdf
What it is used for	Allergic reactions (eg hayfever, itch, rash) Itchy eyes (eg fly bite) Motion sickness (sea or car travel) Nausea and vomiting Sedation (eg penetrating eye injury) Doses
How it works	Allergic reactions are caused by release of a chemical messenger (neurotransmitter) called histamine Antihistamines reduce the body's response to allergy by blocking histamine receptors Promethazine also blocks other receptors to control nausea and prevent vomiting
Side effects	Sleepy Dizzy Blurred vision Dry mouth Confusion Constipation Neuroleptic malignancy syndrome — life threatening reaction presenting with mental status change, rigidity, fever, and increase heart rate, BP and breathing
Warnings	Children under 2 years Old people Liver trouble Epilepsy (fits) Breathing trouble Medical consult if needed for more than one week
Tell the patient	Do not drive or operate machinery if sleepy Do not drink alcohol (grog) — will make you more sleepy Return to clinic if needed for more than a short time Warning stickers: 1
Check	Give by deep IM injection Avoid IV use Do not give SC May cause tissue necrosis — stop injection if there is burning, swelling or pain at injection site Anti-histamines are stopped 4 days before allergy skin-prick testing