title: Amphotericin B is cytotoxic at locally delivered concentrations.
abstract: BACKGROUND
  Orthopaedic fungal infections are commonly treated with systemic amphotericin, which has a narrow therapeutic index and is associated with systemic toxicities. Local delivery of amphotericin has been described yet is poorly understood. As with bacterial infections, fungal infections are associated with biofilm. However, it is unclear whether experience with local delivery of antibacterials can be applied to local antifungal delivery.
  
  
  OBJECTIVE
  We asked whether (1) 100 to 1000 μg amphotericin/mL caused osteoblast cell death; (2) 1 to 10 μg amphotericin/mL caused sublethal toxicity to osteoblasts and fibroblasts; and (3) sublethal amphotericin toxicity could be reversed.
  
  
  METHODS
  Mouse osteoblasts and fibroblasts were exposed in vitro to amphotericin concentrations of 0, 1, 10, 100, and 1000 μg/mL for 5 hours or 0, 1, 5, and 10 μg/mL for 7 days and then 3 days with no amphotericin. Cell morphology on light microscopy and proliferation assays (alamarBlue(®) and MTT) were used as measures of toxicity.
  
  
  RESULTS
  Amphotericin concentrations of 100 μg/mL and above caused cell death; 5 to 10 μg/mL caused abnormal cell morphology and decreased proliferation. Cells regained normal morphology and resumed cell proliferation within 3 days after removal of amphotericin.
  
  
  CONCLUSIONS
  In this in vitro study, amphotericin was cytotoxic to osteoblasts and fibroblasts at concentrations achievable by local delivery.
  
  
  CONCLUSIONS
  If local concentrations of 100 to 1000 times the minimum inhibitory concentration are necessary to treat biofilm-associated fungal infections as they are for bacterial infection, cell toxicity at the local depot site should be considered.
authors.affiliation: Banner Orthopaedic Residency, Banner Good Samaritan Medical Center, 1300 N 12th Street, Suite 620, Phoenix, AZ 85006, USA.
authors.forename: Samuel
authors.initials: S
authors.lastname: Harmsen
authors.forename: Alex C
authors.initials: AC
authors.lastname: McLaren
authors.forename: Christine
authors.initials: C
authors.lastname: Pauken
authors.forename: Ryan
authors.initials: R
authors.lastname: McLemore
mesh_terms: D000666:Amphotericin B / Q000633:toxicity*; D000818:Animals; D000935:Antifungal Agents / Q000633:toxicity*; D041702:BALB 3T3 Cells; D018441:Biofilms / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D013778:Tetrazolium Salts / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism
chemical_list: D000935:Antifungal Agents; D013778:Tetrazolium Salts; D013844:Thiazoles; D000666:Amphotericin B; C022616:thiazolyl blue