Antibiotic-Induced Neutropenia in Patients Receiving Outpatient Parenteral Antibiotic Therapy: a Retrospective Cohort Study.

Our research objective was to describe the incidence and management of antibiotic-induced neutropenia in patients receiving outpatient parenteral antibiotic therapy (OPAT) at our institution over a 7-year period. We conducted a retrospective cohort study of patients followed by the OPAT clinic from 1 July 2016 to 30 March 2022 who developed antibiotic-induced neutropenia (defined as an absolute neutrophil count of ≤1.5 × 10/L). Patients receiving vancomycin in the OPAT clinic received weekly laboratory monitoring, while those receiving other antibiotics received laboratory monitoring at week 3 of therapy. Out of the 2,513 treatment courses, 55 cases of antibiotic-induced neutropenia were identified, resulting in an incidence of 2.2 cases per 100 treatment courses (95% confidence interval [CI], 1.7 to 2.9). Of the 45 cases for which a sole cause was identified, the three most common intravenous antibiotic culprits were vancomycin (21/541; 3.9%), ceftriaxone (10/490; 2.0%), and cloxacillin (2/103; 1.9%). Five (9.1%) patients had symptoms accompanying neutropenia that warranted hospital admission. There were no deaths, and all patients recovered their neutrophil count after antibiotic discontinuation or completion. In nine cases (16.3%), the culprit beta-lactam antibiotic was changed to another beta-lactam agent containing a structurally different side chain, with successful recovery of the neutrophil count in 9/9 (100%). The highest risk of antibiotic-induced neutropenia was associated with vancomycin, ceftriaxone, and cloxacillin in our cohort. With standardized outpatient monitoring during the third week of OPAT, cases of neutropenia can be detected early and managed without hospitalization. Data from our study also support the safety of switching to alternate beta-lactams with structurally different side chains.