Pharmoeconomics of Penicillin Skin Testing (PST) on Inpatient Antibiotic Use in Patients with Penicillin Allergy (PA)

Abstract

RATIONALE: Penicillin is frequently cited on inpatients self-reported drug allergies. PST is a reliable and useful diagnostic tool to determine the risk of an immediate systemic allergic reaction. Pharmoeconomic analysis of PST on inpatients with PA requiring antimicrobial therapy is limited. METHODS: A retrospective chart review of 30/120 inpatients (ages 19-92) consulted for PST between January 2001 to June 2005 was done. Prick and intradermal testing to minor and major (Pre-Pen) determinants was performed. Therapeutic changes implemented as a result of PST, reduction in cost of antibiotics, and adverse reactions were assessed. Cost analysis was based on the hospital cost of antibiotics. RESULTS: 87% (26/30) of subjects had PST (-) 10% (3/30) refused PST, and 3% (1/30) had a PST (-). 85% (22/26) subjects with PST (-), had antimicrobials switched to beta-lactam, 4 (15%) didn't receive beta-lactams. The average cost of antibiotics prior to PST was $4,767 that decreased to $3,864 (19%). Pre-PST prescribed regimens included vancomycin/gentamycin ($10/day,n=4), and quinolones ($18/day,n=5). With piperacillin/tazobactam ($52/day,n=3), there was an increase in cost, but when naficillin ($11/dayn=4), or cephalosporins ($10-15,n=3) were used, switching to beta-lactams proved to be cost effective and decreased broad spectrum antibiotics use. There were no adverse reactions in the PST (-) group of patients who received beta-lactams. 92% of PST (-) patients were still listed as PA on their discharge sheets. CONCLUSIONS: Inpatient PST contributed to changes in antimicrobial therapy from broad spectrum agents to beta-lactams, with a decrease in therapy cost.