Drug Allergy
Key Messages
Drug allergy can be immediate or delayed, and can be allergic or non-allergic.
Clinical history and documentation of the reaction is paramount.
For patients with suspected drug allergy document in the medical records
1. The generic drug name
2. The features and severity of the reaction
3. The date the reaction occurred
Document all new reactions promptly and thoroughly to assist in future investigation.
NICE guidance on drug allergy
Assessment
Immediate, rapidly evolving reactions
Anaphylaxis – a severe multi-system
Onset usually less than 1 hour after drug
reaction characterised by:
exposure (previous exposure not always
• erythema, urticaria or
confirmed)
angioedema
and
• hypotension and/or
bronchospasm
See separate guidance for anaphylaxis
Urticaria or angioedema without
systemic features
Exacerbation of asthma (for example,
with non-steroidal anti-inflammatory
drugs [NSAIDs)
Non-immediate reactions without systemic involvement
Widespread red macules or
Onset usually 6–10 days after first drug
papules (exanthema-like)
exposure or within 3 days of second exposure
Fixed drug eruption (localised
inflamed skin)
Non-immediate reactions with systemic involvement
Drug reaction with eosinophilia and systemic
Onset usually 2–6 weeks after
symptoms (DRESS) or drug hypersensitivity
first drug exposure or within 3
syndrome (DHS) characterised by:
days of second exposure
• widespread red macules, papules or
Version: 2
Date last edited: 23/04/15
Locality: Devon wide
Amendments by: Kevin Bishop
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erythroderma
fever
lymphadenopathy
liver dysfunction
eosinophilia
Toxic epidermal necrolysis or Stevens–Johnson
syndrome characterised by:
• painful rash and fever (often early signs)
• mucosal or cutaneous erosions
• vesicles, blistering or epidermal detachment
• red purpuric macules or erythema multiforme
Onset usually 7–14 days after
first drug exposure or within 3
days of second exposure
Acute generalised exanthematous pustulosis (AGEP) Onset usually 3–5 days after
characterised by:
first drug exposure
• widespread pustules
• fever
• neutrophilia
A drug reaction is more likely if it occurred during or after use of the drug and:
- the drug is known to cause that type of reaction or
- the person has previously had a similar reaction to that drug or drug class
A drug reaction is less likely if:
- there is a possible non-drug cause for the person's symptoms (for example,
they have had similar symptoms when not taking the drug) or
- there were gastrointestinal symptoms only
When a person presents with new suspected drug allergy, document the reaction in
a structured approach (NICE guidance recommendation 1.2.3) including:
a. the generic and proprietary name of the drug or drugs suspected to
have caused the reaction, including the strength and formulation
b. a description of the reaction
c. the indication for the drug being taken (if there is no clinical diagnosis,
describe the illness)
d. the date and time of the reaction
e. the number of doses taken or number of days on the drug before onset
of the reaction
f. the route of administration
g. which drugs or drug classes to avoid in future
Investigations
None recommended prior to referral. Specific IgE (RAST) testing to drugs should
not be used in a non-specialist setting (NICE guidelines).
Version: 2
Date last edited: 23/04/15
Locality: Devon wide
Amendments by: Kevin Bishop
Management
1. Anaphylaxis should be treated immediately according to Resuscitation
Council guidelines. Acute measurement of mast cell tryptase (immediately
and 2 hours after the onset of symptoms) should be performed.
2. The suspected causative drug should be stopped immediately and avoided
pending further investigation if necessary
3. Promptly document the reaction thoroughly, with at minimum
a. The drug name
b. The signs, symptoms, and severity of the reaction
c. The date the reaction occurred
4. Explain the allergy to the patient, and documented in the medical records with
appropriate details.
a. If there is a clear history consider identification jewellery.
b. Advise patients to avoid drugs identified from history as likely causes of
reactions
Referral
Referral criteria
1. Suspected anaphylaxis
2. A severe non-immediate cutaneous reaction
3. NSAID reactions involving urticaria, angioedema, or an asthmatic reaction to
a non-selective NSAID
4. Beta lactam allergy when
a. Beta lactams are considered essential for management
b. There is likely to be frequent need for beta-lactam antibiotics in the
future (eg recurrent bacterial infections or immune deficiency)
c. There is suspected allergy to at least one other class of antibiotics in
addition to beta lactams
5. Suspected local anaesthetic allergy where a procedure involving local
anaesthetic is needed
6. Anaphylaxis or another suspected allergic reaction during or immediately after
general anaesthesia
7. There is diagnostic uncertainty or multiple drugs were involved (especially
where the reaction is systemic)
All information regarding reactions, timing and implicated drugs must be included in
the referral.
General anaesthetic drug reactions should be referred to Dr Sarah Ford and Dr Paul
Sice, Department of Anaesthesia at Derriford Hospital
Referral Instructions
Version: 2
Date last edited: 23/04/15
Locality: Devon wide
Amendments by: Kevin Bishop
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Refer to Peninsula Immunology and Allergy Service
Refer via DRSS for NEW Devon CCG patients
Choose and Book Selection
Specialty: Allergy
Clinic type: Allergy
Service: DRSS- Western –Allergy & Immunology - CCG - 99p
Referral forms
DRSS Referral form
Supporting Information
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2222.2008.03155.x/pdf
http://www.nice.org.uk/guidance/cg183/chapter/recommendations#assessment-2
Patient information
Evidence
Pathway Group
This guideline has been signed off by the Western Locality on behalf of NEW Devon
CCG.
Publication date: June 2015
Review date: May 2017
Version: 2
Date last edited: 23/04/15
Locality: Devon wide
Amendments by: Kevin Bishop