The Immediate and Delayed Maximal Nonirritating Skin Testing Concentrations of β-Lactam Antibiotics

Area of Science:

• Pharmacology
• Allergy and Immunology
• Dermatology

Background:

• Guidelines for maximal skin testing (ST) nonirritant concentrations (NICs) of penicillin and aminopenicillin are consistent.
• Variability exists among guidelines for maximal ST NICs of cephalosporins.

Purpose of the Study:

• To determine maximal immediate and delayed ST NICs for 15 beta-lactam antibiotics.
• To evaluate these NICs in both beta-lactam-tolerant and beta-lactam-naïve participants.

Main Methods:

• A single-center, nonrandomized prospective study involving 747 adult participants.
• Skin prick testing (SPT) and intradermal testing (IDT) with 6 increasing concentrations of beta-lactams.
• Irritancy defined as >5% positive tests; positive test criteria established for immediate and delayed readings (dIDT).

Main Results:

• All undiluted SPT concentrations were nonirritant.
• Maximal IDT/dIDT NICs were determined for 15 beta-lactams, with dIDTs generally nonirritant at higher concentrations.
• No significant differences in results were observed using alternative IDT positivity criteria.

Conclusions:

• SPTs using undiluted beta-lactam stock concentrations are nonirritant.
• Proposed maximal IDT and dIDT NICs are 2- to 50-fold higher than previously published values.
• Higher concentrations are recommended for dIDTs compared to IDTs.