title: A comparative evaluation of adverse platelet outcomes among Veterans' Affairs patients receiving linezolid or vancomycin.
abstract: OBJECTIVE
  The primary objectives were to compare the incidences of severe thrombocytopenia, critical thrombocytopenia and a relative decline in platelets from baseline (≥50% decline) between patients receiving linezolid and those receiving vancomycin. The secondary objective was to assess the relationship between vancomycin trough concentration and adverse platelet outcomes.
  
  
  METHODS
  A matched cohort study was performed at the Upstate New York Veterans' Affairs Healthcare Network from January 2005 until February 2008. Eligibility criteria were: (i) receipt of linezolid or vancomycin therapy for ≥48 h; (ii) initiation of therapy as an inpatient; and (iii) baseline platelets available for evaluation. Patients who received linezolid were matched 1:1 to patients who received vancomycin. Cumulative incidences and times to event for (i) platelet count ≤50,000 cells/mm(3), (ii) platelet count ≤20,000 cells/mm(3) and (iii) ≥50% decline in platelets from baseline were evaluated. Multivariate analyses were performed.
  
  
  RESULTS
  The study included 502 patients (251 matched pairs). The occurrences of platelet counts ≤50,000 cells/mm(3) and ≤20,000 cells/mm(3) did not differ significantly between linezolid and vancomycin patients. A ≥50% decline in platelets from baseline was observed in 78 (31.1%) patients receiving vancomycin and 43 (17.1%) patients receiving linezolid (risk ratio 0.55; 95% CI 0.40-0.77). A clear exposure-response relationship was observed between vancomycin trough concentration and ≥50% decline in platelets from baseline.
  
  
  CONCLUSIONS
  The incidence of thrombocytopenia was low and did not differ significantly among vancomycin and linezolid patients.
authors.affiliation: Albany College of Pharmacy and Health Sciences, Department of Pharmacy Practice, Albany, NY 12208, USA.
authors.forename: Nimish
authors.initials: N
authors.lastname: Patel
authors.forename: Hillary
authors.initials: H
authors.lastname: VanDeWall
authors.forename: Linda
authors.initials: L
authors.lastname: Tristani
authors.forename: Antonio
authors.initials: A
authors.lastname: Rivera
authors.forename: Benjamin
authors.initials: B
authors.lastname: Woo
authors.forename: Amanda
authors.initials: A
authors.lastname: Dihmess
authors.forename: Hsin K
authors.initials: HK
authors.lastname: Li
authors.forename: Raymond
authors.initials: R
authors.lastname: Smith
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Lodise
mesh_terms: D000081:Acetamides / Q000008:administration & dosage* / Q000009:adverse effects*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000009:adverse effects*; D001792:Blood Platelets / Q000187:drug effects; D015331:Cohort Studies; D006801:Humans; D015994:Incidence; D000069349:Linezolid; D008297:Male; D008875:Middle Aged; D009518:New York; D023303:Oxazolidinones / Q000008:administration & dosage* / Q000009:adverse effects*; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000453:epidemiology; D016896:Treatment Outcome; D014640:Vancomycin / Q000008:administration & dosage* / Q000009:adverse effects*
chemical_list: D000081:Acetamides; D000900:Anti-Bacterial Agents; D023303:Oxazolidinones; D014640:Vancomycin; D000069349:Linezolid