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Penicillin Allergy
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Penicillin Allergy
, Penicillin Adverse Drug Reaction, PEN-FAST, Penicillin Allergy Decision Rule
See Also
Penicillin
History
Reaction
How old were you when you had the reaction?
Did Type 1
Hypersensitivity Reaction
symptoms occur?
Anaphylaxis
Hypotension
Laryngeal edema (
Wheezing
or
Stridor
)
Angioedema
Urticaria
How soon after the medication did the reaction start?
Within one hour suggests
Type 1 Hypersensitivity
Was the
Penicillin
given orally or parenterally?
Did the reaction resolve after stopping the medication?
Have you taken related medications and did you react?
Amoxicillin
or
Augmentin
?
Cephalosporin
Evaluation
PEN-FAST Penicillin Allergy Decision Rule
Indications
Penicillin Allergy reported by patient
Criteria: FAST
Score 2 Points (F)
Five years or less since reaction
Score 2 Points (AS)
Anaphylaxis
or
Angioedema
OR
Severe cutaneous adverse reaction
Stevens Johnson Syndrome
Toxic Epidermal Necrolysis
Drug Reaction with Eosinophilia and Systemic Symptoms
(
DRESS Syndrome
)
Acute Generalized Exanthematous Pustulosis
Severe delayed rash with mucosal involvement
Score 1 Point (T)
Treatment required for reaction
Interpretation
Total Score 0 Points
Very low risk of positive Penicillin Allergy test (<1%)
Total Score 1-2 Points
Low risk of positive Penicillin Allergy test (5%)
Total Score 3 Points
Moderate risk of positive Penicillin Allergy test (20%)
Total Score 4-5 Points
High risk of positive Penicillin Allergy test (50%)
Efficacy
PEN-FAST Total Score 0
Negative Predictive Value
(NPV): 99.4%
PEN-FAST Total Score <3
Negative Predictive Value
(NPV): 96.3%
Precautions
IV
Penicillin
reactions were not fully evaluated in study
Rule has not be evaluated in ethnically diverse populations
Other serious reaction histories (e.g.
Interstitial Nephritis
,
Serum Sickness
) were not evaluated in the study
References
Trubiano (2020) JAMA Intern Med 180(5): 745-52 [PubMed]
Management
Cephalosporin
s have cross reactivity with
Penicillin
s
Cross reactivity was originally over-estimated as high as 10% in the 1960s
Attributed to cross contamination
Co-production of
Cephalosporin
s and
Penicillin
s in the same factory
Cephalosporin
reaction when Penicillin Allergy
Penicillin Allergy and allergy to first and
Second Generation Cephalosporins
: 1%
Penicillin Allergy and allergy to
Third Generation Cephalosporins
: Negligible
Aminopenicillins
(
Amoxicillin
and
Ampicillin
) allergy
Cross-reactivity to first and
Second Generation Cephalosporins
: High
R1-side chain of
Aminopenicillins
are similar to first and
Second Generation Cephalosporins
Reaction rate is as high as 27% for
Cefadroxil
Campagna (2012) J Emerg Med 42(5): 612-20 [PubMed]
Penicillin Allergy when
Cephalosporin
allergic: >25%
Cephalosporin
cross reactivity risk factors
Type I
Hypersensitivity
to
Penicillin
Positive
Penicillin
skin test (5% risk)
First or second generation
Cephalosporin
Atopic Dermatitis
Reaction not consistent with Type I
Hypersensitivity
Consider Penicillin
Skin Testing
for allergy
Continue to avoid
Penicillin
s unless otherwise directed by allergy
Consultation
Cephalosporin
s may be used
Some recommend penicillin
Skin Testing
before use
Kelkar (2001) N Engl J Med 345:804-9 [PubMed]
Type I
Hypersensitivity Reaction
Obtain Penicillin
Skin Testing
for allergy
Penicillin
skin test negative (80-95% of cases)
Cephalosporin
s may be used (1.3% risk of reaction)
Continue to avoid
Penicillin
s unless otherwise directed by allergist
Penicillin
skin test positive
Avoid
Penicillin
s and
Cephalosporin
s
Risk of
Cephalosporin
reaction: 4.4%
Consider cephalosporin
Desensitization
Complications
Documented Penicillin Allergy is associated with adverse events due to alternative antibiotic use
Confirm allergy and document actual
Penicillin
reaction
Results in overuse of broad spectrum agents
Associated with longer hospital stay and increased C. Diff and
MRSA Infection
s
Macy (2014) J Allergy Clin Immunol 133(3): 790-6 +PMID:24188976 [PubMed]
References
(2017) Presc Lett 24(3)
Kelkar (2001) N Engl J Med 345:804-9 [PubMed]
Salkind (2001) JAMA 285:2498-505 [PubMed]
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