Drug Allergy - SPS · PDF fileDrug allergy: immune-mediated ... • Penicillin causes 0.7%...
Transcript of Drug Allergy - SPS · PDF fileDrug allergy: immune-mediated ... • Penicillin causes 0.7%...
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Drug Allergy
Alice Oborne PhD,
Consultant pharmacist-safe medication practice and MSO
Medicines Use and Safety Network, 6 November 2014
Objectives
• Demographics
• Immediate and delayed reactions
• Allergy questions – Allergy vs ADR
• Documentation
• Written information to patients
• Referrals for allergy testing
• Steps to keep us all safe
– “Stop and check”
Allergy vs adverse drug reaction: definitions
Allergy
• Inappropriate immune-mediated response to a harmless substance
Drug allergy: … immune-mediated reaction to medicinal product
Current draft NICE guideline definition
• …Any reaction caused by a drug with clinical features compatible with an immunological mechanism
Differs from Adverse Drug Reaction:
• An unwanted or harmful reaction experienced following the administration of a drug or combination of drugs under normal
conditions of use, suspected to be drug related
Page 3Drug allergy: demographics
• Most commonly due to penicillins
• No precise prevalence data
• 10-20% of hospitalised patients report a penicillin allergy
– Of these 1-10% are genuinely allergic
• Penicillin causes 0.7% to 10% of all cases of anaphylaxis
• Risk of anaphylaxis is 0.004% and 0.015% for each course
National data from NRLS, April 12 - March 13
15907Total
12287No Harm
2771Low
828Moderate
14Severe
7Death
Number of reportsDegree of Harm to Patient
With thanks to D Cousins and C Rosario, NHSE
100%15907Grand Total
<1%27Supply or use of over-the-counter medicine
<1%71Advice
1%232
Preparation of medicines in all locations /
dispensing in a pharmacy
2%267Monitoring / follow-up of medicine use
4%647Other
46%7288Administration / supply from a clinical area
46%7375Prescribing
Percentage (%)
Number of
reportsMedication Process
National data 2, Stage of Medication Use Process
77Grand Total
1Incorrect documentation of drug allergy
5No known previous drug allergy
15Unclear if previous unknown allergic reaction
56 (73%)
Drug prescribed/administered even with documented
allergy
Frequency
Did an error occur when the patient had a previous
known allergy?
National data 3, Thematic analysis: allergy known?
77Grand Total
1Antiplatelet
1Metoclopramide
1Alcohol wipes
1Xray contrast
1Antihistamine
1Penicillamine
1Gelofusine
1Plasma substitute
1Anti-epileptic
2Excipient
2Chemotherapy/ Cytotoxic
2Unknown
1Codeine
5Anaesthesia
2NSAID
5Opioid
1Tetracycline
1Trimethoprim
3Cephalosporin
44 (57%)Penicillin
FrequencyTherapeutic Group
National data 4, Thematic analysis: Drug involved
1. Immediate reactions, rapidly evolving: anaphylaxis; urticaria or
angiooedema with hypotension or bronchospasm
2. Non-immediate reactions without systemic involvement
• Acute generalised exanthematous pustulosis or fixed drug eruptions
3. Non-immediate reactions with systemic involvement
• Drug reaction with eosinophilia and systemic symptoms (DRESS)
• Drug hypersensitivity syndrome (DHS)
• Toxic epidermal necrolysis (TEN)
• Stevens-Johnson syndrome (SJS)
4. Common disorders caused rarely by drug allergy
• Eczema, hepatitis, photosensitivity, vasculitis
Practical classification of drug allergy Page 8
• Usually type I hypersensitivity
• Occur quickly after a single dose of drug
• Mast cell degranulation, releasing histamine
• Anaphylaxis
• Urticaria
• Angioedema
• Airway compromise
• Or hypotension
Classification1. Immediate reactions Page 9
Classification2. Non-immediate reactions
• Type IV hypersensitivity
• Can take 6-10 days to develop (earlier with subsequent exposures)
No systemic involvement, lower mortality e.g.
• Rash
• Morbilliform
• Exanthematous
• Maculopapular
Classification: 2. Non-immediate severe: Stevens-Johnson Syndrome
• High mortality
• Desquamation
• Mucosal membrane involvement
• Systemic symptoms
Classification: 2. Non-immediate severe:
Toxic Epidermal Necrolysis (TEN)
• High mortality
• Desquamation
• Mucosal membrane involvement
• Systemic symptoms
Questions to establish allergy or adverse drug reaction
1. What drug(s) is suspected?
2. What was time between ingestion/administration of drug and onset of reaction?
3. Was nature of the reaction in keeping with known adverse reactions to drug?
4. If a rash, what is the nature of the rash?
5. Was there swelling? Where (e.g. facial swelling, lips)?
6. Was there respiratory compromise (difficulty breathing) or in maintaining blood
pressure?
7. Was there any other systematic reaction: liver, renal function abnormalities?
8. Did reaction resolve when the drug was stopped?
9. Responded to antihistamines, steroids?
10.Re-challenge: did reaction recur with re-exposure?
11.Were other drugs administered concurrently that could have caused reaction?
12.Did patient have any underlying condition(s) that could explain reaction?
If in doubt, ask a senior colleague
Allergy vs Adverse drug reaction
• Allergy likely:
• Symptoms of urticaria, angioedema, difficulty in breathing and hypotension occurring within one hour of the last dose of drug
• Non-urticarial rash occurring during a course or within a couple of days of completing a course of the during
• Allergy less likely:
• Symptoms not associated with typical allergic reactions, eg headache, tiredness, migraines etc
• Symptoms are recognised side-effects of the drug, eg bronchoconstriction with beta-blockers, gastritis with NSAIDs, diarrhoea with antibiotics
Use either:
• Drug allergy or
• None known or
• Unable to ascertain
Record, as a minimum:
• Drug name
• Nature of reaction
• Date of reaction
• Ensure visible to all healthcare professionals who use medicines
• Record allergies and ADRs separately
• Check, and update if needed, at every patient contact
• Check before prescribing, supplying, administering
Recording allergy status in healthcare records Page 15
Document new suspected allergic drug reactions in a structured
approach that includes:
• Generic and proprietary drug name
• Description of the reaction
• Indication for which drug was taken
• Date/time of reaction
• Number doses taken or number of days before symptoms onset
• Route
• Drug(s) or classes to avoid in future
Documenting and sharing information with other HCPS
Recording Allergy or ADR: Guys and St Thomas
1. On prescription charts (inpatient, out patient, electronic)
2. All patient records (Electronic patient record, clinical notes, casualty card)
3. Red name band (on same limb as identity band)
4. Communication with other health care professionals (GP, Community Nursing Team)
Check with patient (or carer):
• Before prescribing
• Pharmacy screen / dispensing
• Administration
NICE recommends record allergies and ADRs separately (not currently possible at Guys & St Thomas)
Check and update allergies and confirm with patient (or carers) before
prescribing, dispensing, administering any drug
Ensure that information about drug allergies is included in all
• GP referral letters
• Hospital discharge letters
• Prescriptions issued in any healthcare settings
Implications for
• design of hand-written and electronic discharge letters, and linked e-records
• Handwritten outpatient letters / recommendations to prescribe
• FP10s and linked GP e-records
Maintaining and sharing drug allergy information Page 18
• Discuss suspected allergy with patient (+ parent/ carers)
• Provide written information
• Ensure patient is aware of drug / classes to avoid
• Advise to check with pharmacist before taking OTC medicines
• Record clinician name and date information was given
Information from allergy testing specialist, in writing:
• Diagnosis (allergic or not)
• Drug name and description of reaction
• Investigation performed to confirm/exclude the diagnosis
• Drugs to avoid
• Any safe alternatives
Providing information and support to patients Page 19
General: refer
• Suspected anaphylactic reaction
• Severe non-immediate cutaneous reaction e.g. DRESS, TEN, SJS
Suspected beta lactam antibiotic allergy: refer if
• Needs treatment for disease which can only be treated with beta lactam
• High likelihood of frequent future need for beta lactams e.g. recurrent bacterial
infection or immune deficiency
Suspected NSAID allergy: refer if
• Symptoms such as severe angioedema or asthmatic reactions but needs NSAID
• Asthma with nasal polyps are likely to have NSAID-sensitive asthma
Suspected general anaesthetic allergy: refer if
• Suspected allergic reaction or anaphylaxis during or immediately after GA
Suspected local anaesthetic allergy:
Non-specialist management and referral to specialist services Page 20
Skin testing
• Validated for very few drugs
• Penicillins
• Neuromuscular blocking agents (NMBAs)
• Platinum salts
• Some drugs consistently give false –ve results
• NSAIDs
• Some drugs consistently give false +ve results
• Morphine
• Erythromycin
• NMBAs at high concentration on intradermal testing
NSAID reactions and Selective COX-2 inhibitors
•Advise patient to avoid non-specific NSAIDs including OTC
•May consider selective COX-2 inhibitor if mild reaction to non-specific NSAID if anti-inflammatory is essential
• Discuss with patient first
• Single dose on first day
• Start at low dose
• Only if mild previous reactions
Page 22NICE Guidance on NSAIDs
• After suspected drug-related anaphylactic reaction, take bleed samples for
mast cells tryptase in line with recommendations in Anaphylaxis guideline 134
• Record in notes and on pathology request form the exact timing of samples
• Ensure that tryptase sampling tubes are available in emergency anaphylaxis kits
Serum specific Immunoglobulin E
• Do not use blood IgE for diagnosing drug allergy in non-specialist settings
Measuring serum tryptase after suspected anaphylaxis
Summary
1. New NICE guideline
2. Claimed drug allergy is common, true allergy is rarer but may be fatal
• Not possible to identify which patients have true allergy
3. Classification: Immediate, delayed (mild), delayed (severe)
• Ensure incomplete allergy statements are completed
• Ensure allergies are communicated at transfer
• Document allergies on all prescribing or drug recommendation documents
• NATURE of the reaction and date where known
• Written information to patients on what drugs to avoid
• Refer severe reactions, anaesthetic reactions and beta lactam reactions if likely to need beta lactams in future or if needed now
• Design of e-systems, paper prescriptions, FP10s,
Interventions to help keep patients safe
• Stickers on drug charts (or visible allergy statement in all sections of EPMA)
• Alert on drug cupboards, electronic cabinets “contains penicillin or similar, check allergies”
• - or separate storage if conventions cupboards with advice/warning poster on outside
• Colour coded antibiotic policy
• Drug chart layout (cut away)
• Allergies more visible on ePR and Electronic prescribing (but not yet linked)
• “STOP and check” concept
• Mnemonic for Microbiologist staff giving advice: SAFE: Status and Allergy, Antibiotic–choice, Follow guidelines, don’t use Excessive gentamicin dose
• Colour-coded antimicrobial guidelines (red for penicillins)
• Purchasing: only products with “contains penicillin” on outer packaging
• Pharmacy dispensing label (“contains penicillin”)
• Alert on
• Generic prescribing- increases likelihood of recognising drug is a beta-lactam
• Information – posters, plastic lanyard cards, screensavers,
• Trust Allergy Policy and Procedure
PENICILLIN ALLERGIC Penicillin type drugs include: co-amoxiclav (Augmentin), meropenem, Tazocin