Background: The UNC Medical Center Outpatient Parenteral Antimicrobial Therapy (OPAT) program was started in 2015 to provide multidisciplinary monitoring and management of patients discharged on parenteral antimicrobials. Laboratory abnormalities are a frequent complication of antimicrobial therapy, as are drug reactions such as rash and diarrhea. We examined characteristics of incident adverse drug reactions (ADRs) observed among patients receiving parenteral vancomycin therapy over a two year period.
Methods: This was a retrospective cohort study of patients enrolled in the UNC OPAT program who received vancomycin July 2015-August 2017. Patients with end stage renal disease receiving hemodialysis were excluded. The primary outcome was time-to-first ADR during the first 42 days of vancomycin therapy, estimated using Kaplan-Meier methods. Secondary outcomes included type of ADR and time-to-first nephrotoxicity ADR (>50% increase in serum creatinine). We also assessed indication for OPAT, comorbidities, and concomitant medications among patients with an ADR.
Results: 116 patients were followed on vancomycin therapy for 3367 person-days (~111 person-months). Risk of any ADR within the first 42 days of vancomycin therapy was 33% (95% CI 24%-42%) (Figure 1); risk increased steadily by 6%-8% during the first four weeks on vancomycin therapy. The 42-day risk of nephrotoxicity was 18% (95% CI 10%-26%) (Figure 1), and followed a similar trajectory to overall ADR risks over time on OPAT. Other ADR risks (%) were: neutropenia (<1000 cells/mm3), 5%; rash, 4%; thrombocytopenia (<100×103 cells/mm3 and decrease >50%), 2%; and other, 7%. The most common indications for OPAT vancomycin were osteomyelitis (53%), joint infection (16%), and bacteremia (10%). The most common comorbidities were hypertension (54%) and diabetes (40%). Among patients who experienced an ADR, the most frequent concomitant medications included: NSAID, 62%; ertapenem, 27%; ACE-I, 24%; loop diuretic, 17%; and ARB, 12%.
Conclusion: Risk of ADR increases with duration of parenteral vancomycin therapy during OPAT. Nephrotoxicity was the most common type of ADR during vancomycin therapy. Use of concomitant nephrotoxins during OPAT vancomycin therapy should be evaluated.
V. Chundi, None
C. Farel, None
A. Marx, None
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