Outpatient Parenteral Antibiotic Therapy: More Readmissions, Switches with Oxacillin

PHILADELPHIA, PA—Outpatient treatment with parenteral antimicrobial therapy with beta-lactam antibiotics is effective; however, antibiotic switches for adverse events (AEs) occurred more frequently with oxacillin use, a retrospective study concluded at IDWeek 2014.

“Readmission avoidance should count towards the value of outpatient parenteral antimicrobial therapy (OPAT) programs,” suggested Boeun Lee, MD, of the Department of Geographic Medicine and Infectious Diseases at Tufts Medical Center, Boston, MA. Dr. Lee and colleagues said that although beta-lactam antibiotics are commonly used in OPAT, there are limited data on outcomes of long-term therapy.

The investigators conducted a retrospective cohort study and reviewed the charts of all patients discharged from their institution with cefazolin, ceftriaxone, ertapenem, or oxacillin between 2009 and 2011. Treatment success, readmission, and antibiotic switch rates in patients treated with these antibiotics as outpatient parenteral antimicrobial therapy were compared.

Demographics, infections, antibiotics, outcomes and AE were recorded. Using competing risks analysis, the cumulative incidence of first occurrence of 30-day readmission, antibiotic switch, or treatment success for each drug was compared.

A total 1,028 patients with OPAT courses were identified, and 628 were excluded due to other antibiotic use, loss during follow-up, or other infections. Of the 400 OPAT patients included, 38 received cefazolin; 104 received ceftriaxone; 128 received ertapenem; and 130 received oxacillin.

Treatment success rates were found to be higher for ceftriaxone (81%) and ertapenem (73%), compared with cefazolin (66%) or oxacillin (56%) (Chi-square, P<0.001).

They found 30-day all-cause readmissions to be similar, 21% for cefazolin, 13% for ceftriaxone, 20% for ertapenem, and 15% for oxacillin (P=0.39), as were readmissions for worsening infections or AEs (cefazolin, 5.6%; ceftriaxone, 3.7%; ertapenem, 6.1%, and oxacillin, 5.3%).

Antibiotic switch rates were significantly higher for oxacillin (21.4%) compared with the other agents: 8.3% for cefazolin, 4.1% for ceftriaxone, and 1.8% for ertapenem (P<0.001). Switches due to AEs were more common than treatment failure (n= 31 vs. n=7). In 400 courses of OPAT, 38 antibiotic switches were accomplished without readmission.

“By overseeing antibiotic switches, outpatient parenteral antibiotic therapy programs may avoid adverse event-related readmissions, reducing patient morbidity and costs,” concluded Dr. Lee.