Case 4 - penicillin allergy Flashcards
Consequences of allergy ‘mis-labelling’
best antibiotics may be withheld unnecessarily, with data showing detrimental effect on clinical outcomes
increased healthcare costs
increased drug resistant bacteria
Types of hypersensitivity/allergy [to penicillin]
4 types
Type 1 – immediate (within 1 hour), IgE mediated
Type 4 – delayed (days or weeks), T-cell mediated
Type I hypersensitivity is of most concern - it may proceed to anaphylaxis.
Characteristics of an IgE-mediated (Type 1) reaction - 3 bullet points
Occur immediately or usually within one hour, possible reactions include:
Urticaria (hives)
Angioedema
Wheezing and shortness of breath
Anaphylaxis
Can be predicted by skin tests
[Incidence of Type I penicillin hypersensitivity is <0.05%. Up to 20% of drug-related anaphylaxis deaths in Europe are caused by penicillin]
characteristics of Delayed (Type 4) penicillin hypersensitivity reactions - name 2
Rash
Destruction of RBC, WBC, platelets
Generally develops days to weeks
into drug
NOT predicted by skin tests
Stevens Johnson Syndrome (SJS) - what about it?
A Type IV hypersensitivity reaction that typically involves the skin and the mucous membranes.
Reported with beta-lactams, sulphonamides and other drugs
A serious systemic (body-wide) allergic reaction with a characteristic rash involving the skin and mucous membranes, including the buccal mucosa (inside of the mouth), conjunctiva, and genital areas.
appears 1 to 3 weeks after exposure
Medical emergency and can be life-threatening
name the types of beta-lactams
Penicillins [this includes penicillin, flucloxacillin, amoxycillin; and may be combined with beta-lactamase inhibitors (eg co-amoxiclav)]
Cephalosporins
(Mono-bactams)
Carbapenems
antibiotic used for MRSA and G+
Vancomycin
antibiotics used for only G+
penicillin
flucloxacillin
amoxycillin
antibiotic used for G+ and G-
cephalosporins
antibiotic used for G+, G- and anaerobes
Co-amoxiclav (Augmentin)
antibiotic used for G+, G-, anaerobes and Pseudomonas
piperacillin/tazobactam (Tazocin)
antibiotic used for G+, G-, anaerobes, Pseudomonas and ESBL (resistant E.coli and Klebsiella mainly)
[ESBL - Extended-Spectrum Beta-Lactamase]
carbapenems
antibiotic used for only anaerobes
metronidazole
antibiotic used for only G-
gentamicin
antibiotic used for Pseudomonas and ESBL (resistant E.coli and Klebsiella mainly)
[ESBL - Extended-Spectrum Beta-Lactamase]
gentamicin
Managing beta-lactam allergy
Patients who have experienced a type I allergic reaction with penicillins should not be prescribed beta-lactam agents including penicillins, cephalosporins, or carbapenems.
Cephalosporins and carbapenems: can use with caution in patients that do not have a history of a type I mediated allergic reaction.
