Beta lactam 3

• removing the allergy label from their medical records if testing or clinical history shows they are not actually allergic

delabelling

• not life-long

• not truly allergic

• true allergy - life threatening

pencillin allergies

• Avoidance of penicillins that are safe, cheap, and effective.

• Inappropriate avoidance of all beta-lactams, including cephalosporins.

• Reliance on alternative antibiotics that may be more toxic.

• Increased use of broad-spectrum antimicrobials, which drives the emergence of multi-resistant bacterial strains.

• Leads directly to poorer clinical outcomes for patients.

having pencillin allergy label

• Increased use of broad-spectrum antibiotics

• Increased C. difficile rate

• Increased length of stay

• Increased mortality

• Increased risk of surgical site infection

• Increased monetary costs

• Prolonged time to first dose of antibiotics

disadvantages of penicllin allergies

• Three epitopes

pencillin as allergen

• R2 side chain is lost after opening

  of the beta-lactam ring, with IgE antibodies recognising the R1

  and part of the beta-lactam ring structure

cephalosporins as allergens

• : Interview patients with an antibiotic allergy label and document a detailed allergy history (essential even if the patient does not currently have an infection).

• Patient Education: Educate patients about the negative consequences of unverified antibiotic allergy labels.

• Label Delabeling: Remove or delete labels if they are inappropriate (e.g., non-allergic side effects).

• Clarification: Clarify specific allergy details and identify antibiotics that have been tolerated.

• Prescriber Support: Assist doctors and prescribers with selecting appropriate alternative antibiotics for patients with true antibiotic allergies.

pharmacists role in allergy

• Mechanism: Non-immune mediated adverse drug reactions that are pharmacologically predictable.

• Nature: Not true allergic reactions.

• Severity Levels: Can present as severe or non-severe.

• Management (Non-Severe): Allergy labels should be directly removed from medical records after a discussion with the patient. e.g. nausea, vomiting

• Management (Severe): The implicated drug should be avoided. However, it may still be possible to use other drugs within the same pharmacological class. - renal impairment, encephalitis

• 
  

type A reactions

• Caused by the presence of antibiotic-specific IgE bound to basophils and mast cells.

  • Occurs within minutes of exposure to a parenteral drug.

  • Occurs within 1–2 hours of oral ingestion.

  • A longer delay indicates a lower likelihood of the reaction being IgE-mediated.

• 
  

Immediate IgE-mediated reactions

• Activation of antibiotic-specific T-cells leading to downstream activation of macrophages, neutrophils, or eosinophils.

• Formation of antibody/antigen immune complexes.

• Unknown mechanisms.

• Timing of Onset:

  • Can occur at any time after 1 hour from initial drug administration.

  • Most commonly occurs $>72$ hours after administration, but can present up to days or weeks following exposure.

Delayed (non-immediate) adverse reactions

• no treatment required or

  ‾ oral non-sedating anti-histamines and/or

  ‾ short course of topical or oral steroids

managing mild-moderate symptoms

• hospitalisation

  ‾ adrenaline

  ‾ resuscitation and ICU support may be required

managing severe symptoms

• Name the implicated agent using its generic name (e.g., 'amoxicillin') rather than broad categories; never label a patient as allergic to the entire drug class (e.g., 'penicillins').

• Timing of Event: Provide the date or timeframe when the reaction took place (e.g., >10 years ago, as a child).

• Reaction Details: Record specific features of the reaction, including:

  • What occurred

  • When it occurred

  • Severity of the reaction

  • Treatment provided

• Tolerated Alternatives: List any antibiotics successfully tolerated since the initial reaction occurred.

documentation of allergy antibiotics

Isolated GI upset (diarrhoea, nausea, vomiting, abdominal pain)

• Chills (rigors)

• Headache

• Fatigue

• Thrush

• Family Histories -

no risk of allergy

• Childhood rash

• Unknown, remote (>5–10 years ago) reaction

• MRE (Maculopapular Rash/Exanthem)

low risk allergy

• Throat tightness

• Shortness of breath

• Wheezing

• Angioedema/swelling

• Hypotension

• Bronchospasm

moderate risk allergy

• Anaphylaxis

• Delayed T-Cell Mediated Reactions:

  • DRESS: Drug Reaction with Eosinophilia and Systemic Symptoms (rash with eosinophilia and organ injury)

  • SJS/TEN: Stevens-Johnson Syndrome / Toxic Epidermal Necrolysis (rash with mucosal lesions)

  • Serum Sickness: Rash with joint pain, fever, and myalgia

  • Hematologic Reactions: Thrombocytopenia, leukopenia

  • AGEP: Acute generalised exanthematous pustulosis (rash with pustules)

• Prevalence:

  • 11.9% fall into high risk phenotypes (BCV Antibiotic Allergy Delabelling Program).

• Recommended Clinical Action:

  • Refer to a Drug Hypersensitivity Clinic — do NOT test.

high risk allergy

• penfast tool

assessing allergy

• Non-immune mediated adverse reactions (Type A reactions) are not true allergic reactions.

  • Examples include gastrointestinal symptoms such as nausea, vomiting, and diarrhoea.

• Reported allergies may actually reflect a family history rather than an individual reaction.

• The patient may have successfully tolerated the antibiotic since the initial concerning reaction occurred.

• These allergy labels should be directly removed from medical records without the need for skin testing or an oral challenge.

• Delabeling must take place after a discussion with the patient or carer.

• Clinicians should explain the nature of the reaction and discuss the potential risks—such as treatment failure and adverse events—associated with unnecessarily avoiding these antibiotics.

direct delabelling

• Low-dose penicillin oral challenge can be considered if there is a distant allergy history ( 5- 10years ago) and either of the following criteria are met:

  • Onset of mild, isolated, non-progressive symptoms (such as rash or hives alone)

  • OR unknown clinical history with no features of a severe reaction

• Challenge Protocols: Protocols may involve a one-step, two-step, three-step, or prolonged (e.g., 3-day) challenge.

• Agent Selection:

  • Selection of the specific oral penicillin challenge agent is critical (e.g., amoxicillin vs. phenoxymethylpenicillin).

  • For an unknown allergy occurring prior to 1970, phenoxymethylpenicillin is appropriate.

Penicillin oral challenge

• prior to an oral challenge is required for moderate-to-high severity IgE reactions.

• Test Controls & Reagents:

  • Positive control: Histamine

  • Negative control: Saline

  • Allergen: Penicillin (major and minor determinants)

• Administrator Requirement: Should only be performed by clinical immunology and allergy specialists due to the risk of anaphylaxis and the complexity of interpreting results.

skin testing