Penicillin Anaphylaxis : A Dreaded Drug Reaction

Penicillin or Beta lactam antibiotics are commonly associated with drug reactions which are immunologically mediated reactions.

Why does penicillin anaphylaxis occur?

The core structure Beta lactams consists of a reactive bicyclic B lactam ring that acts as a hapten by covalently binding to tissue carrier proteins. 95% of tissue bound penicillin is found to be haptenated in the form of benzyl penicilloyl which is called the major determinant and 5% of tissue bound penicillin consist of 3 non-crossreactive metabolites called the minor determinants.

Most often immediate allergic reactions are caused by major determinants.

Sometimes modified penicillin such as ampicillin can produce allergic reaction in which the antigenic determinant is the side chain.

What are the manifestations of pencillin allergy?Penicillin anaphylaxis

  1. Difficulty breathing or dyspnea
  2. Wheezing due to bronchospasm
  3. Drop in blood pressure (Hypotension)
  4. Swelling of the throat or tongue (Angiodema)
  5. Dizziness
  6. Loss of consciousness
  7. Rapid or weak pulse
  8. Pruritis, Urticaria
  9. Abdomen cramping, diarrhea

What precautions should be taken?

  1. Skin testing by an allergist
  2. Shared cross-reactivity can occur with cephalosporins, monobactams and carbapenams
  3. Peolple who expereinced symptoms with penicllin previously like following should be more cautious:
  • Rash, itching, urticaria, fever
  • Wheezing, angioneuritic edema, serum sickness, exfoliative dermatitis

Treatment:

  • Epinephrine or Adrenaline administration
    • 0.3-0.5 mL 1:1000 soln SC or IM q15min
    • 0.5-1 mL 1:10,000 soln IV; slow administration; repeat prn
    • 0.3-0.5 mL 1:1000 soln SL q15min
    • 1 mL 1:1000 soln ET in approximately 10 mL NS
    • IV infusion: 0.1-1 mcg/kg/min
  • Airway management
  • Inhaled beta-agonists
  • Volume expansion by IV fluids
  • Antihistaminics
  • Corticosteroids
  • Glucagon

Detail reading on treatment of anaphylaxis @ Medscape

Reference: Washington Manual of Medical Therapeutics 32nd edition

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