title: Potency and stability of frozen urokinase solutions in syringes.
abstract: OBJECTIVE
  The stability and potency of frozen urokinase solutions in syringes were studied.
  
  
  METHODS
  To determine the stability and potency of compounded urokinase dilutions after multiple freeze-thaw cycles, a total of 160 syringes containing five urokinase concentrations (2,500, 5,000, 7,500, 12,500, and 25,000 IU/mL) were prepared. For each of the five concentrations tested, two syringes per concentration were reserved for baseline testing. The remaining 150 syringes were frozen at -30 degrees C. After 7 days, half of the syringes (group 1) were thawed at room temperature, tested, and left at room temperature for 12 hours before refreezing. The other half of the syringes (group 2) were kept frozen for 30 days. Thirty days after initial compounding, all syringes were thawed, and the samples' urokinase potency, pH, and physical appearance were evaluated. Syringes were visually inspected for color, clarity, and precipitation. Descriptive statistics were computed for each concentration group and testing day.
  
  
  RESULTS
  The compounded dilutions were stable under each experimental condition, with no physical deterioration or loss of in vitro potency after two freeze-thaw cycles. The reduced waste associated with the ability to refreeze unused urokinase could substantially lower the cost of procedures such as thrombolysis after intraventricular hemorrhage and catheter clearance by as much as 95%.
  
  
  CONCLUSIONS
  Dilutions of urokinase 2,500-25,000 IU/mL were stable in single-use syringes after being frozen for 7 days, thawed, and refrozen for another 23 days.
authors.affiliation: Sterile Product Area, Duke University Medical Center, Durham, NC, USA.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Dedrick
authors.forename: José
authors.initials: J
authors.lastname: Ramirez-Rico
mesh_terms: D004339:Drug Compounding; D004355:Drug Stability; D004356:Drug Storage; D005615:Freezing; D006863:Hydrogen-Ion Concentration; D007275:Injections, Intravenous; D019999:Pharmaceutical Solutions; D010969:Plastics; D013053:Spectrophotometry; D013594:Syringes; D013997:Time Factors; D014568:Urokinase-Type Plasminogen Activator / Q000737:chemistry* / Q000191:economics
chemical_list: D019999:Pharmaceutical Solutions; D010969:Plastics; D014568:Urokinase-Type Plasminogen Activator