Extended-Interval Aminoglycoside Dosing for Treatment of Enterococcal and Staphylococcal Osteomyelitis

Abstract

BACKGROUND: Gram-positive osteomyelitis requires long-term antibiotic therapy, much of which is often administered in the outpatient setting. Historically, synergistic aminoglycoside use in these infections requires multiple daily doses, which can be inconvenient. Data regarding extended-interval aminoglycoside dosing (EIAD), also known as once-daily dosing, in this setting are lacking. OBJECTIVE: To evaluate the safety and efficacy of EIAD in the treatment of gram-positive osteomyelitis. METHODS: Retrospective chart review of adult patients treated for documented, gram-positive osteomyelitis with EIAD at the University of New Mexico Home IV Antibiotic Clinic was conducted. The patients' medical records were reviewed by an infectious diseases clinical pharmacist. Clinical and microbiologic outcomes and the incidence of nephrotoxicity and ototoxicity were the main outcome measures. RESULTS: Fifteen patients (16 events) were included. Enterococcus spp. was the most common organism isolated. Nine patients had infected equipment or devices; 6 of these had removal of these devices in conjunction with antibiotic therapy. The median duration of antibiotic therapy was 6 weeks (range 6–31). The median duration of aminoglycoside therapy was 28 days (range 6–43). Seven patients developed nephrotoxicity, 5 of whom received an aminoglycoside in combination with vancomycin. Male patients had a higher risk of developing nephrotoxicity compared with females (p = 0.04). The mean ± SD duration of EIAD before the development of nephrotoxicity was 34 ± 8 days. Clinical cure was achieved in 12 (75%) patients. Three patients achieved clinical cure without hardware removal. CONCLUSIONS: Most of the patients with gram-positive osteomyelitis were successfully managed with EIAD. However, nephrotoxicity developed in a high proportion of patients and was likely related to prolonged aminoglycoside use.