Allergy/Anaphylaxis

Question 1

What type of anti-allergic/anaphylactic is promethazine?

Answer 1

Sedating antihistamine

Question 2

What is the mode of action of promethazine?

Answer 2

Reduce the effects of histamine by binding to the H1 receptor and stabilising it in an inactive form.

They also have anticholinergic activity, some have alpha-blocking activity (eg promethazine) and some have antiserotonin activity (eg cyproheptadine).

Question 3

What are the indications for promethazine?

Answer 3

Allergic conditions, eg rhinitis, urticaria

Itch

Nausea and vomiting, including motion sickness

Sedation (short term)

Question 4

What are the contraindications for promethazine?

Answer 4

Phenylketonuria – some contain aspartame

Epilepsy – lowers the seizure threshold.

Respiratory depression – may worsen

Parkinson’s disease – symptoms may worsen (promethazine may have some antidopaminergic activity); use an alternative antihistamine or monitor carefully.

Question 5

What are the adverse effects for promethazine?

Answer 5

Sedation

Psychomotor impairment

Dizziness

Confusion

Headache

Blurred vision

Mydriasis

Dry eyes

Constipation

Dry mouth

Urinary retention

Question 6

What is the route of administration for promethazine?

Answer 6

IM injection