title: Is insulin diluted when stored in water?
abstract: Insulin storage is a challenge in resource-poor countries. In Uganda, patients were noted to store insulin vials by submerging them in water.
  
  
  
  To examine whether withdrawing insulin from a vial without adding air back causes a vacuum which allows water to enter the vial, resulting in insulin dilution.
  
  
  
  Seven hundred units of insulin were withdrawn from forty 10 mL vials of 100 units/mL insulin [20 neutral protamine hagedorn (NPH), 20 regular]. In half, air was added back. The vials were weighed (baseline). Half of the vials (10 with added air, 10 without) were submerged in water for 24 h and then air-dried for 24 h. Vials that were not submerged sat at room temperature for 48 h. All vials were weighed 48 h from baseline.
  
  
  
  Addition of air did not impact the change in weight after submersion (air added: -0.002 ± 0.001 g or -0.2 ± 0.1 unit; no air added: -0.003 ± 0.000 g or -0.3 ± 0 unit, p = 0.57). In a subset of vials in which an additional 240 units were withdrawn before submersion for another 24 h, there was still no difference in weight change in those vials with air added (p = 0.2).
  
  
  
  Withdrawing insulin from a vial without adding air did not result in uptake of water or dilution of insulin in the submerged vial, although it made drawing up the insulin easier. This study did not address the larger concern of bacterial contamination of the rubber stopper during water storage.
authors.affiliation: University of Minnesota Masonic Children's Hospital, Minneapolis, MN, USA.
authors.forename: Phillip
authors.initials: P
authors.lastname: Plager
authors.affiliation: College of Science and Engineering, University of Minnesota, Minnesota, MN, USA.
authors.forename: Kadiro
authors.initials: K
authors.lastname: Nurie
authors.affiliation: University of Minnesota Masonic Children's Hospital, Minneapolis, MN, USA.
authors.forename: Trevor
authors.initials: T
authors.lastname: Omann
authors.affiliation: University of Minnesota Masonic Children's Hospital, Minneapolis, MN, USA.
authors.forename: Antoinette
authors.initials: A
authors.lastname: Moran
authors.affiliation: Department of Pediatrics, College of Health Sciences, Makerere University, Kampala, Uganda.
authors.forename: Thereza
authors.initials: T
authors.lastname: Piloya
authors.affiliation: Diabetes Centre, St. Francis Nsambya Hospital, Kampala, Uganda.
authors.forename: Silver
authors.initials: S
authors.lastname: Bahendeka
authors.affiliation: University of Minnesota Masonic Children's Hospital, Minneapolis, MN, USA.
authors.forename: Muna
authors.initials: M
authors.lastname: Sunni
mesh_terms: D003080:Cold Temperature; D003906:Developing Countries; D060766:Drinking Water / Q000737:chemistry; D004340:Drug Contamination / Q000191:economics / Q000517:prevention & control; D004349:Drug Packaging; D004356:Drug Storage / Q000191:economics; D006801:Humans; D007004:Hypoglycemic Agents / Q000032:analysis / Q000737:chemistry* / Q000191:economics; D007328:Insulin / Q000032:analysis / Q000737:chemistry* / Q000191:economics; D007336:Insulin, Isophane / Q000032:analysis / Q000737:chemistry* / Q000191:economics; D009994:Osmolar Concentration; D010539:Permeability; D011204:Poverty Areas; D012034:Refrigeration / Q000191:economics; D015203:Reproducibility of Results; D012408:Rubber / Q000737:chemistry*; D000074822:Treatment Adherence and Compliance; D014454:Uganda
chemical_list: D060766:Drinking Water; D007004:Hypoglycemic Agents; D007328:Insulin; D007336:Insulin, Isophane; D012408:Rubber
keywords: insulin dilution; insulin storage; submerged insulin