Download Allergy - Australian Medicines Handbook

1
Allergy
See also Allergic rhinitis p 393, Allergic conjunctivitis
p 464, Eczema p 346, Asthma p 801
Anaphylactic reactions
Are severe hypersensitivity reactions with rapid
development of life-threatening respiratory and/or
circulation problems, often with skin and mucosal
changes. Clinical presentation is variable.
Triggers include foods (including additives, eg
metabisulfite), drugs, insect stings, blood products,
latex (eg surgical gloves). Symptoms may appear
within minutes to several hours of exposure (eg
onset after IV exposure may be faster than after oral
exposure).
The risk or severity of anaphylactic reactions may
be affected by other factors, such as exercise,
infections, other diseases (eg asthma), drugs (eg
NSAIDs), alcohol.
There are no clinically relevant differences between
anaphylactic reactions that are allergic (mediated
by IgE or other immune complexes) or non-allergic
(non-immune mediated).
Rationale for drug use
Prevention of serious complications and death.
Cardiorespiratory support.
Symptom relief.
Drug treatment
See Table 1–1 Management of anaphylaxis p 2
All health care facilities should have an anaphylaxis protocol; refer to this where available.
Evidence for treatments used for anaphylactic
reactions is derived from clinical practice; trial data
are generally lacking.
Note that some treatments used may themselves
cause anaphylactic reactions, eg volume expanders
such as dextran and polygeline (Haemaccel®,
Gelofusine®).
Adrenaline
IM injection into the mid-anterolateral thigh is
safe and effective and should be used at the first
suspicion of an anaphylactic reaction.
When used with volume expansion, adrenaline
usually restores BP and cardiac output to acceptable levels; additional vasopressor agents are
occasionally indicated.
IV adrenaline should only be given by those
experienced in its use, with continuous monitoring of ECG, pulse oximetry and BP as it has a
high risk of adverse effects.
SC route is not recommended because absorption is erratic.
Nebulised adrenaline may be useful in upper
airway obstruction, eg laryngeal oedema, but
should not delay intubation in progressive
airway obstruction.
First
give IM adrenaline 1:1 000 into mid-anterolateral thigh,
dose 10 micrograms/kg (0.01 mL/kg) up to maximum
500 micrograms (0.5 mL):
• adult, child >50 kg, 500 micrograms (0.5 mL adrenaline
1:1 000)
• 40 kg, 400 micrograms (0.4 mL adrenaline 1:1 000)
• 30 kg, 300 micrograms (0.3 mL adrenaline 1:1 000)
• 25 kg, 250 micrograms (0.25 mL adrenaline 1:1 000)
• 20 kg, 200 micrograms (0.2 mL adrenaline 1:1 000)
• 15 kg, 150 micrograms (0.15 mL adrenaline 1:1 000)
• 10 kg, 100 micrograms (0.1 mL adrenaline 1:1 000)
Then
• remove cause if practical, eg insect sting, stop an IV
infusion
• give high flow oxygen (>6 L/minute via face mask)
• ensure supine position, with elevated legs if tolerated (if
breathing is difficult, allow to sit but not to stand)
• establish IV access
• maintain airway, breathing and circulation (do not delay
intubation in progressive airway obstruction)
If hypotensive
• give IV sodium chloride 0.9% by rapid infusion:
– adult, 1–2 L
– child, 20 mL/kg
– repeat if inadequate response
If inadequate response
• continue to give IM adrenaline every 3–5 minutes
• if unresponsive to IM adrenaline and ECG monitoring is
available, consider IV adrenaline infusion (safer than IV
bolus), see local protocols
If response still inadequate, consider
• nebulised adrenaline for upper airway tract obstruction
(stridor)
• inhaled (via MDI and spacer) or nebulised salbutamol for
lower airway tract obstruction (wheeze)
• IV glucagon (p 70) for persistent hypotension in people
taking beta-blockers
• additional vasopressors for persistent hypotension
Monitor
• pulse rate, BP, respiratory rate (ECG, pulse oximetry,
arterial blood gases if possible)
• for 4–6 hours after recovery; extend period if severe or
refractory symptoms, history of severe asthma or lifethreatening or biphasic reactions, or possibility of
continuing absorption of trigger
Glucagon
Case reports indicate that glucagon (p 70) may
help persistent hypotension in patients on betablockers (who may be refractory to adrenaline).
Corticosteroids
These have a delayed effect (4–6 hours).
Although they are generally used to reduce
duration of reaction and prevent relapse, there is
no evidence of effectiveness; they may be helpful
for asthmatics. They are adjuncts in the management of anaphylaxis and should not be used
instead of adrenaline.
IV fluids
Antihistamines
Required to expand intravascular volume and
restore BP in combination with adrenaline.
There is no evidence that H1 antagonists (eg
promethazine) and H2 antagonists (eg ranitidine) are effective in acute anaphylaxis (parenteral promethazine may worsen condition).
They are adjuncts helpful for associated urticaria, angioedema and itch.
Beta2 agonists
Inhaled (via MDI and spacer) or nebulised shortacting beta2 agonists may help relieve
bronchospasm that is resistant to adrenaline.
2
Table 1–1 Management of anaphylaxis
AMH © 2012
1.1 Sympathomimetics
Further management
• biphasic reactions, where symptoms recur after
apparent recovery, may occur; their incidence is
unclear (reported rates range from 1–23%) and
there is no way to reliably predict which patients
are at risk
• serum mast cell tryptase samples may help
confirm the diagnosis; collect samples as soon as
possible after presentation, and 1–2 hours and
24 hours after symptoms started
• after recovery, obtain detailed history of
symptoms (particularly timing of exposure to
trigger with respect to reaction) and possible
triggers; update medical records if necessary;
refer patient for specialist review
• in people at risk of recurrent anaphylaxis:
– provide an action plan and review it
regularly; see www.allergy.org.au
– provide up to 2 adrenaline autoinjectors if
needed and train the person and their carers
on their use; ensure they have a repeat supply
of the adrenaline autoinjector if it has been
used
– if a specific trigger is identified from history
or skin testing, advise avoiding further
exposure and wearing a warning bracelet or
necklace
– ensure parents of affected children inform all
carers of nature of trigger, symptoms and
signs of a reaction and its treatment (consider
providing a copy of the action plan)
– consider risk–benefit of avoiding betablockers as they may make anaphylaxis
harder to treat
• using an adrenaline autoinjector reduces the
need for subsequent doses and hospital
admissions for children (data are lacking for
adults); effective education may improve poor
rate of use
• consider immunotherapy (desensitisation) for
insect sting allergy
1.1 Sympathomimetics
Adrenaline
For additional information see Adrenaline p 236
See also Anaphylactic reactions p 2
For drug interactions see Adrenaline p 848
Also known as epinephrine.
Indications
Anaphylactic reactions
Bronchospasm and croup
Precautions
There are no absolute contraindications to
adrenaline in anaphylactic reactions; adrenaline is
often life-saving.
Dosage
See also Table 1–1 Management of anaphylaxis p 2
Anaphylaxis
IM route is preferred as it is safer than IV.
IV administration may be necessary when
response to repeated IM doses and volume
AMH © 2012
expansion 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, which
generally should be used for imminent cardiac
arrest.
IM
Adult, child, 10 micrograms/kg (0.01 mL/kg
adrenaline 1:1 000) up to 500 micrograms
(0.5 mL). Repeat every 3–5 minutes if required.
EpiPen®, Anapen®
The following doses 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.
Adult, child >20 kg, IM 0.3 mg.
Child 10–20 kg, IM 0.15 mg.
IV infusion
Adult, child, initially 0.1 micrograms/kg/minute,
then titrate according to response.
Slow IV injection
Adult, 50 micrograms (0.5 mL adrenaline
1:10 000). Repeat according to response. Give IV
infusion if repeated doses required.
Child, initially 1 microgram/kg (0.01 mL/kg
adrenaline 1:10 000). Titrate dose according to
response.
Nebuliser
For upper airway tract obstruction, eg laryngeal
oedema.
Adult, child, up to 5 mL (5 mg) of adrenaline
1:1 000.
Croup
Neb, 0.5 mg/kg (0.5 mL/kg adrenaline 1:1 000);
maximum 5 mg (5 mL).
Administration advice
Use a 0.5 mL or 1 mL syringe to measure small
volumes of adrenaline.
Inject IM adrenaline into mid-anterolateral thigh
(do not inject into buttocks).
For IV bolus, use adrenaline 1:10 000 and give
slowly over at least 5 minutes into the side-arm of
a fast flowing IV infusion.
If 1:10 000 is required and 1:1 000 is the only
strength available, dilute 1 mL of 1:1 000 with 9 mL
of sodium chloride 0.9% to make a 1:10 000
solution.
SC administration is not recommended in
anaphylaxis as absorption is erratic.
Counselling
Make sure anyone who may need to give you
adrenaline is taught how to recognise when you
need it and how to give it.
Call an ambulance as soon as possible after using
adrenaline because further doses may be required.
Keep your adrenaline autoinjector handy. It needs
to be stored in the dark, between 15 and 25C, but
not refrigerated; an insulated carry pouch may be
needed.
Note the use by date for your adrenaline and
arrange a new supply in advance.
3
1
1.2 Antihistamines
1
Practice points
• ampoules contain 1 mg adrenaline, ie:
– adrenaline 1:1 000 = 1 mg in 1 mL
– adrenaline 1:10 000 = 1 mg in 10 mL
• glucagon may be useful for adrenaline-resistant
anaphylaxis in patients on beta-blockers
• EpiPen® and Anapen® have different administration techniques; training devices are available
to assist with education of patients and carers; a
written action plan should be provided
inj, 0.1 mg/mL, 10 mL, 10, Adrenaline 1:10 000 (AS, LM)
inj, 0.1 mg/mL, 10 mL (syringe), 1, Adrenaline 1:10 000 Min-IJet (CS)
inj, 1 mg/mL, 1 mL, 5, 50, Adrenaline 1:1000 (LM), PBS[5]/
DPBS[5]
inj, 1 mg/mL, 1 mL, 5, Adrenaline 1:1000 (AS)
inj, 150 mcg, 0.3 mL, 1, Anapen Juniora (LM), EpiPen Jra (AL),
PBS-A1
inj, 300 mcg, 0.3 mL, 1, Anapena (LM), EpiPena (AL), PBS-A1
1
a
anticipated emergency treatment of anaphylaxis, see PBS
preloaded injector
1.2 Antihistamines
See also Allergic rhinitis p 393, Eczema p 346
Antihistamines are divided into 2 groups: older,
sedating drugs and newer, less sedating drugs; they
have similar efficacy.
Individual response to an antihistamine varies
widely; it may be necessary to try a number to see
which is best tolerated and most effective. See Table
1–2 Comparison of antihistamines p 5.
Practice points
• some antihistamines are available with
decongestants and/or analgesics for relief of pain,
cough, nasal congestion or symptoms of
influenza, the common cold and allergies; there is
little rationale for these combinations; avoid use
1.2.1 Sedating antihistamines
See also Antihistamines p 4
For drug interactions see Antihistamines (sedating)
p 853
Cyclizine p 841
Cyproheptadine p 5
Dexchlorpheniramine p 6
Diphenhydramine p 6
Doxylamine p 6
Pheniramine p 6
Promethazine p 7
Trimeprazine p 7
Mode of action
Antagonise the action of histamine at H1 receptors,
reducing histamine-related vasodilation and
increased capillary permeability.
They also have anticholinergic activity, some have
alpha-blocking activity and some have antiserotonin
activity, eg cyproheptadine.
Indications
Allergic upper respiratory conditions, eg rhinitis
Allergic skin conditions, eg urticaria, contact
dermatitis
Pruritus (including insect bites)
Nausea and vomiting
Precautions
Closed-angle glaucoma, GI obstruction, bladder outlet
obstruction (eg prostatic hypertrophy)—may be
worsened by the anticholinergic effects of antihistamines.
Elderly
Avoid use (less sedating antihistamines preferred
for allergic conditions) or use a lower dose; increased risk of adverse effects, eg dizziness, sedation,
confusion, hypotension, falls, anticholinergic effects.
Children
Avoid use, particularly in children <2 years (less
sedating antihistamines preferred for allergic
conditions); increased risk of adverse effects, eg
sedation, paradoxical stimulation, anticholinergic
effects.
Do not use phenothiazine antihistamines
(promethazine, trimeprazine) in children <2 years;
an association between these antihistamines and
sudden infant death syndrome has been suggested
but not confirmed. Promethazine may cause fatal
respiratory depression.
Pregnancy
Many of these antihistamines have been used
extensively in pregnancy as antiemetics and in
treatment of allergic disorders without evidence of
fetal adverse effects.
Breastfeeding
Limited data but short-term use appears safe.
Sedation of mother is main concern.
Adverse effects
Common
sedation, dizziness, tinnitus, blurred vision,
euphoria, incoordination, anxiety, insomnia, tremor,
nausea, vomiting, constipation, diarrhoea, epigastric
discomfort, dry mouth, cough
Infrequent
urinary retention, palpitations, hypotension,
headache, hallucinations, psychosis
Rare
leucopenia, agranulocytosis, haemolytic anaemia,
allergic reactions, arrhythmias, dyskinesia,
paraesthesia, paralysis, hepatitis
Paradoxical stimulation
CNS stimulation (excitation, hallucinations, ataxia,
seizures) may occur rarely, especially in children,
rather than sedation.
Counselling
This medication may make you sleepy; don’t drive
or operate machinery if this happens.
Avoid alcohol and other medication that may cause
sedation.
Practice points
• response to a specific antihistamine varies widely,
and it may be necessary to try a number of agents
to determine which is best tolerated and most
effective; response to one member of a class does
not predict response to another member of that
class
• avoid use of antihistamines for the symptomatic
treatment of upper respiratory tract infections in
young children because of the self-limiting nature
of the illness and lack of demonstrated benefit
• antihistamines should be stopped at least 4 days
before skin-prick testing
Sedation, eg premedication
4
AMH © 2012
1.2.1 Sedating antihistamines
Table 1–2 Comparison of antihistamines
Class/drug
Adverse effects
Pregnancy Breastfeeding Children
Uses
Products
>2 years
allergy,
itch
tablet, oral
liquid
>5 years
allergy,
itch,
antiemetic
tablet
>2 years
antiemetic
tablet
allergy,
sedation,
insomnia
capsule, tablet,
oral liquid
>12 years
insomnia
capsule, tablet
>2 years
allergy,
itch,
sedation,
premedication,
antiemetic
tablet, oral
liquid, injection
antiemetic
tablet
1
Sedating antihistamines
Alkylamines
brompheniramine1
chlorpheniramine1
dexchlorpheniramine1
pheniramine
fewer sedative and GI
adverse effects than
other sedating antihistamines; more likely to
cause paradoxical CNS
stimulation
not available as a single ingredient
safe
safe to use short
term
Monoethanolamines
occasional dose
safe
dimenhydrinate2
diphenhydramine1
significant sedative
effects; low incidence of
GI adverse effects
safe
>2 years
(for allergy
safe to use short or
term
sedation)
doxylamine1
Phenothiazines
promethazine
hydrochloride1
promethazine
theoclate
most anticholinergic
antihistamines;
safe but
significant sedative
close
effects; may lower seizure avoid
to delivery
threshold and cause
respiratory depression
safe to use short
term
>3 years
least sedating of the
sedating antihistamines;
may increase weight
safe to use short >2 years
term
>2 years
(>3 years
for
sedation)
trimeprazine
urticaria,
itch,
sedation in oral liquid
children
Piperidines
cyproheptadine
safe
allergy,
itch
tablet
Less sedating antihistamines
cetirizine
desloratadine
fexofenadine1
levocetirizine
>1 year
often better tolerated
than sedating antihistamines (reduced sedating
and anticholinergic
safe
effects); cetirizine and
levocetirizine most likely
to cause sedation
safe
loratadine1
1
2
tablet, oral
liquid, oral
drops
allergic
>6 months rhinitis and
conjuncti>6 months vitis,
chronic
urticaria
>12 years
tablet
>1 year
tablet, oral
liquid
tablet, oral
liquid
tablet, oral
liquid
available with decongestants and/or analgesics, see Practice points p 4 in Antihistamines
only available combined with hyoscine hydrobromide (p 494)
Cyproheptadine
Pregnancy
Safe to use; Australian category A.
For additional information see Sedating
antihistamines p 4
For drug interactions see Antihistamines (sedating)
p 853
Adverse effects
Infrequent
Indications
Adult, child >7 years, initially 4 mg 3 times daily;
maximum 32 mg daily (maximum 16 mg daily if
<14 years).
2–6 years, initially 2 mg 2 or 3 times daily;
maximum 12 mg daily.
Allergic conditions, eg rhinitis, conjunctivitis,
urticaria
Pruritus
Precautions
weight gain
Dosage
Depression—cyproheptadine antagonises serotonin
and may occasionally reduce the effectiveness of
SSRIs.
AMH © 2012
5
1.2.1 Sedating antihistamines
1
Practice points
Practice points
• cyproheptadine is still marketed for migraine
and vascular headache but evidence for efficacy
in these indications is limited
• used to treat serotonin toxicity, may shorten
duration of symptoms; no controlled trials; for
moderate-to-severe symptoms a dose of 8 mg
every 6–8 hours if needed, has been suggested
by some specialists
• when used for insomnia:
– do not use for >10 consecutive days
– can cause daytime sedation, psychomotor
impairment and anticholinergic effects; not
recommended for elderly people
– sedative effect declines with continued use
• injection of contents of diphenhydramine
capsules (by drug misusers) may result in
phlebitis, infection or more serious local effects
tab, 4 mg (scored, white), 100, Periactin (AS), PBS-R1
1
prevention of migraine
Dexchlorpheniramine
For additional information see Sedating
antihistamines p 4
For drug interactions see Antihistamines (sedating)
p 853
Dexchlorpheniramine is the dextroisomer of
chlorpheniramine.
Indications
Allergic conditions, eg rhinitis, conjunctivitis,
urticaria, contact dermatitis
Pruritus
tab, 50 mg (white), 10, Snuzaid (WD)
cap, 50 mg (clear), 10, Snuzaid Gels (WD)
cap, 50 mg (blue), 10, Unisom Sleepgels (PP)
oral liquid, 2.5 mg/mL, 120 mL, Children’s Paedamin
Antihistamine (CP)
Doxylamine
For additional information see Sedating
antihistamines p 4
See also Insomnia p 778
For drug interactions see Antihistamines (sedating)
p 853
Indications
Short-term management of insomnia
Precautions
Pregnancy
Accepted
Safe to use; Australian category A.
Precautions
Pregnancy
Dosage
Adult, child >12 years, 2 mg 4 times daily.
6–12 years, 1 mg 4 times daily.
2–6 years, 0.04 mg/kg 3 times daily.
tab, 2 mg (scored, white), 20, 40, Polaramine (SH)
oral liquid, 0.4 mg/mL, 100 mL, Polaramine Syrup (SH)
Diphenhydramine
For additional information see Sedating
antihistamines p 4
See also Insomnia p 778
For drug interactions see Antihistamines (sedating)
p 853
Indications
Allergic conditions, eg rhinitis, conjunctivitis,
urticaria
Sedation (short term)
Short-term management of insomnia
Precautions
Pregnancy
Safe to use; Australian category A.
Dosage
Adult, child >12 years
Allergy, 25–50 mg every 4–6 hours as required.
Sedation, 50 mg as a single dose.
Insomnia, 50 mg at night.
Nausea and vomiting in pregnancy
Safe to use; Australian category A.
Dosage
Adult
Insomnia, 25–50 mg 30 minutes before bedtime.
Nausea and vomiting in pregnancy, initially 12.5 mg
at night; increase dose to 12.5 mg twice daily if
needed.
Practice points
• when used for insomnia:
– do not use for >10 consecutive days
– can cause daytime sedation, psychomotor
impairment and anticholinergic effects; not
recommended for elderly people
– sedative effect declines with continued use
tab, 25 mg (scored, white), 20, Dozile (KY), Restavit (WD)
cap, 25 mg (purple), 20, Dozile (KY)
Pheniramine
For additional information see Sedating
antihistamines p 4
For drug interactions see Antihistamines (sedating)
p 853
Indications
2–6 years
Allergic conditions, eg rhinitis, conjunctivitis,
urticaria, contact dermatitis
Pruritus
Motion sickness
Nausea, vomiting and vertigo due to Ménière’s
disease
Allergy, 6.25 mg every 4–6 hours as required.
Sedation, 1 mg/kg single dose.
Precautions
Pregnancy
6–12 years
Allergy, 12.5 mg every 4–6 hours as required.
Sedation, 1 mg/kg single dose (maximum 50 mg).
6
Safe to use; Australian category A.
AMH © 2012
1.2.1 Sedating antihistamines
Dosage
Motion sickness
For motion sickness, take the first dose 30 minutes
before travel.
Adult, child >10 years, initially, 22.65 mg (half a
45.3 mg tablet) 2 or 3 times daily; up to 45.3 mg
3 times daily.
5–10 years, 22.65 mg (half a 45.3 mg tablet) up to
3 times daily.
Adult, child >12 years, oral 25 mg the night before
or 2 hours before travel. Repeat dose after
6–8 hours if required.
Child >2 years, oral 0.5 mg/kg the night before or
2 hours before travel.
Sedation
tab, 45.3 mg (scored, white), 10, 50, Avil (AV)
Adult, child >12 years, oral 25–75 mg once daily
or IM 25–50 mg single dose.
Child >2 years, IM/oral 0.5 mg/kg, single dose.
Promethazine
Premedication
Phenothiazine
For additional information see Sedating
antihistamines p 4
See also Nausea and vomiting p 488
For drug interactions see Antihistamines (sedating)
p 853
Adult, IM 25–50 mg 1–2 hours before procedure.
Promethazine theoclate
Nausea and vomiting
Adult, 25 mg 2 or 3 times daily to a maximum of
100 mg; 25 mg at bedtime may be sufficient.
Motion sickness
Adult, child >10 years, 25 mg 1–2 hours before
travel. For long journeys take 25 mg each night
beginning the night before travelling.
5–10 years, 12.5 mg given as above.
3–5 years, 6.25 mg given as above.
Promethazine theoclate is also known as
promethazine teoclate.
Indications
Allergic conditions, eg rhinitis, conjunctivitis,
urticaria, contact dermatitis
Pruritus
Nausea and vomiting, including motion sickness
Sedation, eg for cases of burns, measles, chickenpox
Premedication
Precautions
Phenylketonuria—Gold Cross Antihistamine Elixir®
contains aspartame; avoid use.
Epilepsy—promethazine lowers the seizure
threshold.
Respiratory depression—may worsen.
Pregnancy
Safe to use; avoid close to delivery due to
theoretical risk of neurological disturbance in
infant; Australian category C.
Adverse effects
Rare
seizures
Injection
Tissue damage can occur following injection by
any route, but can be particularly severe after
extravasation or intra-arterial or SC injection.
Effects range from pain and burning to thrombophlebitis, paralysis, necrosis and gangrene. See also
Administration advice below.
Dosage
Promethazine hydrochloride
Allergy
Adult, child >12 years, oral 25–75 mg once daily,
or 10–25 mg 2–3 times daily or IM 25–50 mg
single dose.
Child >2 years, IM/oral 0.125 mg/kg 3 times daily,
and 0.5 mg/kg 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.
AMH © 2012
Administration advice
Give by deep IM injection. Avoid IV use; if
necessary, dilute and give into a large vein at a rate
not exceeding 25 mg/minute (avoid extravasation
or intra-arterial injection due to risk of severe
irritation); stop injection immediately if there is
burning, swelling or pain at injection site. Do not
give SC (may cause tissue necrosis).
Promethazine hydrochloride
tab, 10 mg (blue), 50, Fenezal (SZ)
tab, 10 mg (blue), 50, Phenergan (AV), PBS-A1/RPBS
tab, 25 mg (blue), 50, Fenezal (SZ)
tab, 25 mg (blue), 50, Phenergan (AV), PBS-A1/RPBS
oral liquid, 1 mg/mL, 100 mL, Gold Cross Antihistamine Elixir
(BI)
oral liquid, 1 mg/mL, 100 mL, Phenergan Elixir (AV), PBS-A1
inj, 25 mg/mL, 2 mL, 5, Promethazine Hydrochloride (HS),
PBS[10]/DPBS[10]
1
palliative care, see PBS
Promethazine theoclate
tab, 25 mg (scored, white), 10, 30, Avomine (AV)
Trimeprazine
Phenothiazine
For additional information see Sedating
antihistamines p 4
For drug interactions see Antihistamines (sedating)
p 853
Also known as alimemazine.
Indications
Urticaria or pruritus, symptom relief
Sedation in children
Precautions
Epilepsy—trimeprazine lowers the seizure
threshold.
Respiratory depression—may worsen.
Diabetes—oral liquid contains 0.68 g/mL sucrose.
Pregnancy
Safe to use; avoid close to delivery due to theoretical
risk of neurological disturbance in infant; Australian
category C.
7
1
1.2.2 Less sedating antihistamines
1
Dosage
Urticaria or pruritus
Adult, child >12 years, 10 mg 3–4 times daily;
maximum 100 mg daily.
Elderly, 10 mg once or twice daily.
Child >2 years, 0.1–0.25 mg/kg 4 times daily;
maximum 20 mg daily.
Sedation
3–12 years, 1–2 mg/kg at night; maximum 50 mg.
oral liquid, 1.5 mg/mL, 100 mL, Vallergan (AV)
oral liquid, 6 mg/mL, 100 mL, Vallergan Forte (AV)
Cetirizine
For additional information see Less sedating
antihistamines p 8
Indications
Allergic rhinitis and conjunctivitis
Chronic urticaria
Precautions
Allergy to cetirizine, levocetirizine or hydroxyzine—
contraindicated (cetirizine is hydroxyzine’s active
metabolite).
1.2.2 Less sedating
antihistamines
Renal
See also Antihistamines p 4
Use oral drops in children <2 years as the amount
of sorbitol (0.32 g/mL) in the oral liquid may cause
diarrhoea.
Cetirizine p 8
Desloratadine p 8
Fexofenadine p 9
Levocetirizine p 9
Loratadine p 9
Mode of action
Selectively antagonise the action of histamine at
H1 receptors. Histamine release causes vasodilation and increases capillary permeability.
Indications
Allergic rhinitis and conjunctivitis
Chronic urticaria
Precautions
Elderly
Increased risk of sedation and anticholinergic
effects (but preferred to older sedating antihistamines); monitor carefully.
Pregnancy
Safe to use although there is more experience with
older sedating antihistamines. Desloratadine and
loratadine: Australian category B1; cetirizine,
fexofenadine and levocetirizine: Australian
category B2.
Breastfeeding
Safe to use.
Adverse effects
Common or infrequent
drowsiness, fatigue, headache, nausea, dry mouth
Infrequent
elevated liver enzymes, weight gain
Rare
rash, hypersensitivity (eg anaphylaxis, bronchospasm)
Counselling
This medication makes some people sleepy; don’t
drive or operate machinery if this occurs.
Practice points
• there is marked individual variation in response
to any specific antihistamine; there is no
evidence that any one agent is superior
• cetirizine and levocetirizine are the most likely
of the less sedating antihistamines to cause
sedation
• antihistamines should be stopped at least 4 days
before skin-prick testing
8
Reduce dose if CrCl <30 mL/minute.
Children
Adverse effects
Rare
hepatitis, dystonias
Dosage
Adult
10 mg once daily.
Child
>6 years, 10 mg once daily or 5 mg twice daily.
2–6 years, 5 mg once daily or 2.5 mg twice daily.
1–2 years, oral drops, 0.25 mg/kg twice daily.
Renal impairment
Adult, child >6 years, CrCl <30 mL/minute, 5 mg
once daily.
Counselling
Avoid drinking alcohol while taking this medicine.
tab, 10 mg (scored, white), 10, 30, Alzene (AL), Zilarex (SZ),
Zyrtec (JT), RPBS[30]
tab, 10 mg (scored, white), 10, 30, 50, ZepAllergy (IA)
tab, 10 mg (scored, white), 10, 30, Zodac (GM), Cetirizine (TX)
oral liquid, 1 mg/mL, 75 mL, 200 mL, Zyrtec (JT)
oral drops, 10 mg/mL (2.5 mg/5 drops), 20 mL, Zyrtec (JT)
Desloratadine
For additional information see Less sedating
antihistamines p 8
Indications
Allergic rhinitis and conjunctivitis
Chronic urticaria
Precautions
Allergy to desloratadine or loratadine—contraindicated.
Dosage
Adult
5 mg once daily.
Child
6–11 years, 2.5 mg once daily.
1–5 years, 1.25 mg once daily.
6–11 months (chronic urticaria), 1 mg once daily.
tab, 5 mg (light blue), 7, 28, 42, Aerius (SH)
tab, 5 mg (light blue), 7, 28, Claramax (SH)
oral liquid, 0.5 mg/mL, 100 mL, Aerius (SH)
oral liquid, 0.5 mg/mL, 60 mL, Aerius for Children (SH)
AMH © 2012
1.2.2 Less sedating antihistamines
Fexofenadine
For additional information see Less sedating
antihistamines p 8
For drug interactions see Fexofenadine p 889
Indications
Dosage
Adult
Renal impairment
CrCl 30–49 mL/minute, 5 mg on alternate days.
CrCl 10–29 mL/minute, 5 mg once every 3 days.
Allergic rhinitis and conjunctivitis
Chronic urticaria
Counselling
Precautions
Renal
tab, 5 mg (white), 10, 30, Xyzal (UC)
Consider reducing initial dose if CrCl <30 mL/
minute.
Loratadine
Dosage
Adult
Rhinitis
120 mg daily in 1 or 2 doses or 180 mg once
daily.
Urticaria
180 mg once daily.
Child
6 months – 2 years, 15 mg twice daily.
2–11 years, 30 mg twice daily.
CrCl <30 mL/minute
Adult, initially 60 mg once daily.
2–11 years, initially 30 mg once daily.
6 months – 2 years, initially 15 mg once daily.
Counselling
Oral liquid: you can take this medicine with or
without food, but if you take it with a fatty meal, it
may not be absorbed as well.
tab, 30 mg (peach), 20, Fexal (SZ), Fexotabs (AV), Telfast (AV)
tab, 60 mg (peach), 20, Fexotabs (AV)
tab, 60 mg (peach), 20, Fexal (SZ), Telfast (AV), RPBS[60]
tab, 120 mg (peach), 10, 30, Allerfexo (GM), Fexo (AS)
tab, 120 mg (peach), 10, 50, Fexotabs (AV)
tab, 120 mg (peach), 10, 20, 30, Tefodine (AS)
tab, 120 mg (peach), 10, 30, Fexal (SZ), Telfast (AV), Xergic
(AL), RPBS[30]
tab, 180 mg (peach), 10, 30, Fexal (SZ), Fexo (AS), Telfast (AV)
tab, 180 mg (peach), 10, 50, Fexotabs (AV)
tab, 180 mg (peach), 10, 20, 30, Tefodine (AS)
tab, 180 mg (scored, yellow), 10, 30, Allerfexo (GM), Xergic
(AL)
oral liquid, 6 mg/mL, 150 mL, Telfast Children’s Elixir (AV)
1
5 mg once daily.
Avoid drinking alcohol while taking this medicine.
For additional information see Less sedating
antihistamines p 8
Indications
Allergic rhinitis and conjunctivitis
Chronic urticaria
Precautions
Allergy to loratadine or desloratadine—contraindicated.
Hepatic
Reduce starting dose in severe impairment.
Dosage
Adult, child >30 kg
10 mg once daily.
Child
2–12 years, <30 kg, 5 mg once daily.
1–2 years, 2.5 mg once daily.
Severe hepatic impairment
Adult, initially 5 mg once daily.
tab, 10 mg (scored, white), 10, 30, 50, Allereze (AL), Claratyne
(SH), Lorano (SZ), RPBS[30]
tab, 10 mg (scored, white), 10, 30, 50, Alledine (AS), Allerdyne
(GM), Lorastyne (BF), Loratadine (AM, CO)
tab, 10 mg (dispersible, white), 10, Claratyne Effervescent (SH)
oral liquid, 1 mg/mL, 100 mL, 200 mL, Claratyne (SH)
oral liquid, 1 mg/mL, 150 mL, Lorapaed (AE)
Levocetirizine
For additional information see Less sedating
antihistamines p 8
Indications
Allergic rhinitis and conjunctivitis
Chronic urticaria
Precautions
Allergy to levocetirizine, cetirizine or hydroxyzine—
contraindicated (levocetirizine is the active isomer
of cetirizine; cetirizine is hydroxyzine’s active
metabolite).
Renal
Contraindicated if CrCl <10 mL/minute. Reduce
dosing frequency if CrCl 10–49 mL/minute.
AMH © 2012
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