Antihistamines

Question 1

Cyclizine

Answer 1

Prevention of postoperative nausea and vomiting

Adult, IV 25–50 mg approximately 20 minutes before the end of surgery. May be given up to 3 times daily for a maximum of 48 hours after surgery.

Motion sickness, radiotherapy
For motion sickness, take the first dose 1–2 hours before travel.

Adult, child >12 years, oral 50 mg up to 3 times daily.

6–12 years, oral 25 mg up to 3 times daily.

Question 2

Cyproheptadine

Answer 2

Allergy or itch
Adult, child >7 years, oral, initially 4 mg 3 times daily; maximum 32 mg daily (maximum 16 mg daily if <14 years).

2–7 years, oral, initially 2 mg 2 or 3 times daily; maximum 12 mg daily.

Serotonin toxicity
Dose recommendations vary; the following dosage has been suggested for significant agitation and neuromuscular excitation.

Adult, oral 12 mg; may be repeated once if partial response occurs. If treatment of ongoing symptoms is required (eg serotonin toxicity is due to a drug with a long half-life), use 4–8 mg 3 times daily.

Question 3

Dexchlorpheniramine

Answer 3

Adult, child >12 years, oral 2 mg 4 times daily.

6–12 years, oral 1 mg 4 times daily.

2–6 years, oral 500–800 micrograms (1.25–2 mL) 3 or 4 times daily.

Question 4

Diphenhydramine

Answer 4

Allergy
Adult, child >12 years, oral 25–50 mg every 4–6 hours as required.

6–12 years, oral 12.5 mg every 4–6 hours as required.

Insomnia
Adult, oral 50 mg at night.

Sedation
For short-term use under medical supervision. Give as a single dose at night.

Adult, child >12 years, oral 50 mg.

Question 5

Doxylamine

Answer 5

Adult

Insomnia, oral 25–50 mg 30 minutes before bedtime.

Nausea and vomiting in pregnancy, oral, initially 12.5 mg at night; increase dose to 12.5 mg twice daily if needed.

Question 6

Promethazine

Answer 6

Allergy
Adult, child >12 years, oral 25–75 mg once daily, or 10–25 mg 2 or 3 times daily or IM 25–50 mg single dose.

2–12 years, IM/oral 0.125 mg/kg (maximum 12.5 mg) 3 times daily, or 0.5 mg/kg (maximum 25 mg) at night.

Nausea and vomiting

Adult, child >12 years, oral 25 mg or IM 12.5–25 mg every 4–6 hours as needed; maximum 100 mg daily.

2–12 years, oral 0.25–1 mg/kg (maximum 25 mg) every 4–6 hours as needed; maximum 100 mg daily.

Motion sickness
Adult, child >12 years, oral 25 mg the night before or 1–2 hours before travel. Repeat dose after 6–8 hours if required.

2–12 years, oral 0.5 mg/kg (maximum 25 mg) the night before or 1–2 hours before travel. Repeat dose after 6–8 hours if required (maximum 3 doses in 24 hours).

Sedation
For short-term use under medical supervision. Give 1–2 hours before procedure or as a single dose at night.

Adult, child >12 years, oral 25–75 mg.

2–12 years, oral 0.5–1 mg/kg (maximum 25 mg).

Question 7

Bilastine

Answer 7

Adult, child >12 years, oral 20 mg once daily.

Question 8

Cetirizine

Answer 8

Adult, child >12 years
Oral, 10 mg once daily.

Child

6–12 years, oral 10 mg once daily or 5 mg twice daily.

2–6 years, oral 5 mg once daily or 2.5 mg twice daily.

1–2 years, oral drops, 2.5 mg (5 drops) twice daily.

Renal impairment
Adult, child >6 years, CrCl <30 mL/minute, oral 5 mg once daily.

Question 9

Desloratadine

Answer 9

Adult, child >12 years
Oral, 5 mg once daily.

Child
6–12 years, oral 2.5 mg once daily.
1–6 years, oral 1.25 mg once daily.
6 months – 1 year (chronic urticaria only), oral 1 mg once daily.

Question 10

Fexofenadine

Answer 10

Adult, child >12 yearsRhinitis
Oral, 120 mg daily in 1 or 2 doses or 180 mg once daily.

Urticaria
Oral, 180 mg once daily.

Child
2–12 years, oral 30 mg twice daily.
6 months – 2 years (urticaria only), oral 15 mg twice daily.

CrCl <30 mL/minute
Adult, child >12 years, oral, initially 60 mg once daily.
2–12 years, oral, initially 30 mg once daily.
6 months – 2 years, oral, initially 15 mg once daily.

Question 11

Loratadine

Answer 11

Adult, child >30 kg
Oral, 10 mg once daily.

Child
2–12 years, <30 kg, oral 5 mg once daily.
1–2 years, oral 2.5 mg once daily.

Severe hepatic impairment
Initially, give above dose on alternate days.

Question 12

Adrenaline (epinephrine) (anaphylaxis)

Answer 12

Anaphylaxis
IM route is preferred as it is safer than IV.
IV administration may be necessary when response to repeated IM doses is inadequate. However, it should only be given by those experienced in its use and with continuous monitoring of ECG, pulse oximetry and BP. IV infusion is safer than slow bolus. For use in cardiac arrest, see Adrenaline (epinephrine) (cardiovascular).

IM
Adult, child, IM 10 micrograms/kg (0.01 mL/kg adrenaline 1:1 000) up to 500 micrograms (0.5 mL). Repeat every 5 minutes if required.

Autoinjector (eg EpiPen®, Anapen®)

The doses below are recommended by bodies such as the Australasian Society of Clinical Immunology and Allergy; for some children they are higher than the doses recommended by the manufacturer. Repeat dose after 5 minutes if required.

The following doses are for adults and children.
>50 kg, IM 300 micrograms or 500 micrograms.
20–50 kg, IM 300 micrograms.
7.5–20 kg, IM 150 micrograms.

IV infusion
Follow local protocol where available.
Adult, child, IV, initially 0.1 microgram/kg/minute, then titrate according to response.

Nebuliser
For upper airway tract obstruction, eg laryngeal oedema.

Adult, child, neb, up to 5 mL (5 mg) of adrenaline 1:1 000.

Severe croup
>1 month, neb 5 mL of undiluted adrenaline 1:1000 as a single dose. Repeat after 30 minutes if required.