![]() ![]() Benzylpenicillin + its alkaline product (penicilloate) and acid product (penilloate) (optimal reagents for skin testing) are minor determinants: formed less often than penicilloyl, but clinically important.BenzylPenicilloyl poly-L-lysine (PrePen, ALK-Abello, Round Rock, TX), synthetic analog of major antigenic determinant: comprises 95% of tissue-bound penicillin. ![]() Penicillin covalently binds proteins spontaneously under physiologic conditions, enzymatic metabolism is not required.Penicillin allergens derived from core ring structure, bicyclic structure consists of 4-member beta-lactam ring and 5-member thiazolidine ring.Immediate (72hrs) reaction, non-IgE-mediated, multiple underlying immunologic mechanisms.Levine classification based on timing of symptom appearance.Produces contact dermatitis, maculopapular eruptions, eosinophilia, Stevens-Johnson syndrome, exfoliative dermatitis.Type IV, cell-mediated hypersensitivity.IgG- and IgM-mediated, soluble antigen-antibody complexes.Causes interstitial nephritis, thrombocytopenia, or hemolytic anemia.IgG ab binds to drug-haptenated host cells such as renal cells or red blood cells.Produces urticaria, angioedema, laryngeal edema, bronchospasm, hypotension, abdominal distress (per oral).IgE ab bound to basophils and mast cells is cross-linked by drug with subsequent release of mediators: histamine, prostaglandins, proteases, and leukotrienes.Gell and Coombs classification based on immunopathology.Drug-induced hypersensitivity syndrome (DiHS) with multiorgan involvement Drug Reaction/Rash with Eosinophilia and Systemic Symptoms (DRESS).Associated with specific human leukocyte antigen allotypes.Presents as painful new skin eruption, sore throat, and fever or malaise.Mucocutaneous eruption with epidermal detachment: Stevens-Johnson syndrome (30% body surface area).Identification of patients with IgE-mediated allergy or history of severe reaction is paramount.Illness or combination of illness and antibiotic causing symptoms attributed to allergy.Mislabeling of a reaction (e.g., diarrhea) as allergic.Waning of penicillin-specific IgE antibodies over time.But as many as 90% of these can tolerate penicillin. Allergy to one penicillin indicates potential allergy to all penicillins, but cross-reactivity between classes of beta-lactams is variable. Immunologic hypersensitivity reaction to beta-lactam antibiotics. ![]()
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