Skin testing with penicilloate and penilloate prepared by an improved method: Amoxicillin oral challenge in patients with negative skin test responses to penicillin reagents

Background: Penicillin skin testing has been limited by the lack of commercial Objective: This project was proposed to produce a stable, well-characterized supply of penicilloate and penilloate for intrastate use by our health maintenance organization and to document clinical safety and efficacy. Methods: An improved method of extraction for penicilloate and penilloate, which changed the solvents used during recrystallization, was developed, With these newly prepared reagents, penicillin skin testing was performed on 348 subjects. Skin testing was immediately followed by an oral challenge of 250 mg of amoxicillin in 215 of 288 (75%) subjects displaying a negative response to a battery of penicillin skin tests. Results: Nuclear magnetic resonance and mass spectrometry of the newly produced penicilloate and penilloate showed no evidence of organic contamination. Penicillin skin testing resulted in 17.2% (60 of 348) positive test results, with 20% of the subjects with positive results only responding to the newly produced minor determinants, The rate of mild adverse reactions to penicillin skin testing was 1.1% (4 of 348). The rate of mild acute adverse reactions was 5.1% (11 of 215), and the delayed reaction rate was 0.9% (2 of 215) with the amoxicillin challenge. Conclusions: This improved penicillin minor determinant extraction method allows for the reproducible production of very pure preparations of penicilloate and penilloate. Large-scale penicillin skin testing, followed by amoxicillin challenge if results are negative is feasible in a large group model health maintenance organization operating within a single state with the use of internally produced penicilloate and penilloate and commercially available penicillin, amoxicillin, and penicilloyl polylysine.