title: Prediction of inventory sustainability during a drug shortage.
abstract: OBJECTIVE
  A methodology for predicting how long the on-hand inventory of a given medication will last during a supply shortage is described; a practical example of application of the methodology is provided.
  
  
  METHODS
  Single-site data on consumption of i.v. tobramycin over an eight-month evaluation period were collected using commercial software that tabulates barcode-assisted medication administration (BCMA) events; administered doses were standardized as 1200-mg "vial-equivalents" and summed over the review period. The total number of vial-equivalents consumed was divided by the number of "non-zero weeks of consumption" (i.e., weeks during which any tobramycin use occurred) to obtain a mean ± S.D. weekly consumption rate; this rate was multiplied by the total i.v. tobramycin on-hand supply (in vial-equivalents) to determine the mean number of potentially sustainable weeks of therapy in the event a shortage were to restrict the future supply of the drug.
  
  
  RESULTS
  Overall, 99.6 vial-equivalents of i.v. tobramycin were used during the evaluation period. The mean ± S.D. number of vial-equivalents used per non-zero week of consumption was 3.11 ± 1.26. A manual count of pharmacy inventory revealed that 102.9 vial-equivalents were available at the time of analysis. The mean predicted duration of supply was 33 weeks (95% confidence interval, -126 to 192 weeks).
  
  
  CONCLUSIONS
  Available BCMA data on tobramycin consumption over eight months were used to calculate the mean number of weeks the on-hand supply of the drug could be expected to last during a persistent drug shortage.
authors.affiliation: Department of Pharmacy Practice, Midwestern University, Chicago College of Pharmacy, Downers Grove, ILDepartment of Pharmacy, Northwestern Memorial Hospital, Chicago, IL.
authors.forename: Nathaniel J
authors.initials: NJ
authors.lastname: Rhodes
authors.affiliation: Department of Pharmacy Practice, Chicago State University College of Pharmacy, Chicago, ILDepartment of Pharmacy, Northwestern Memorial Hospital, Chicago, IL.
authors.forename: Elise M
authors.initials: EM
authors.lastname: Gilbert
authors.affiliation: Henry Ford Hospital, Detroit, MI.
authors.forename: Erik
authors.initials: E
authors.lastname: Skoglund
authors.affiliation: Department of Pharmacy Practice, Chicago State University College of Pharmacy, Chicago, ILDepartment of Pharmacy, Northwestern Memorial Hospital, Chicago, IL.
authors.forename: John S
authors.initials: JS
authors.lastname: Esterly
authors.affiliation: Department of Pharmacy, Northwestern Memorial Hospital, Chicago, IL.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Postelnick
authors.affiliation: Department of Pharmacy Practice, Midwestern University, Chicago College of Pharmacy, Downers Grove, ILDepartment of Pharmacy, Northwestern Memorial Hospital, Chicago, IL. milgriff@nm.org.
authors.forename: Milena M
authors.initials: MM
authors.lastname: McLaughlin
mesh_terms: D000046:Academic Medical Centers / Q000600:supply & distribution; D000900:Anti-Bacterial Agents / Q000600:supply & distribution*; D001330:Electronic Data Processing / Q000379:methods*; D005544:Forecasting; D006801:Humans; D007445:Inventories, Hospital / Q000379:methods*; D004364:Pharmaceutical Preparations / Q000600:supply & distribution; D014031:Tobramycin / Q000600:supply & distribution*
chemical_list: D000900:Anti-Bacterial Agents; D004364:Pharmaceutical Preparations; D014031:Tobramycin