title: Stability of ceftazidime in a viscous eye drop formulation.
abstract: OBJECTIVE
  To assess the stability of an extemporaneously prepared ceftazidime eye-drop.
  
  
  METHODS
  Ceftazidime was formulated at a concentration of 5% w/v as an eye drop, using Sno Tears, an artificial tear solution containing polyvinyl alcohol, as a vehicle. Two batches of the formulation were stored in 10 ml eye drop bottles at 7 and 25 degrees C for up to 14 days. Ceftazidime and pyridine, its degradation product, were determined at intervals by HPLC.
  
  
  RESULTS
  A yellow coloration was evident after 7 days at 7 degrees C and after 24 h at 25 degrees C. Ceftazidime lost approximately 35% after 7 days storage at 25 degrees C. At 7 degrees C, the mean time to 10% degradation, determined by linear regression, was 11 and 8 days for the two batches. However, the lower 95% confidence limits were 8 and 5 days, respectively. Pyridine levels increased during storage. The mass balance between ceftazidime remaining and pyridine formed was close to 100% during the early part of storage. By the end of storage, the balance had reduced to around 95% at 7 degrees C and 80% at 25 degrees C. This discrepancy may be due to sorption of pyridine to the butyl rubber bottle closure. The pH remained in the range 6-7 throughout the storage period.
  
  
  CONCLUSIONS
  The formulation may be stored for 5 days in the refrigerator.
authors.affiliation: Pharmaceutical Sciences Institute, Aston University, Birmingham, UK. abarnes@dmu.ac.uk
authors.forename: A R
authors.initials: AR
authors.lastname: Barnes
authors.forename: S
authors.initials: S
authors.lastname: Nash
mesh_terms: D002442:Ceftazidime / Q000032:analysis* / Q000737:chemistry*; D002511:Cephalosporins / Q000032:analysis / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D004339:Drug Compounding / Q000379:methods; D004355:Drug Stability; D006863:Hydrogen-Ion Concentration; D016014:Linear Models; D009883:Ophthalmic Solutions / Q000737:chemistry*; D011142:Polyvinyl Alcohol / Q000737:chemistry; D011725:Pyridines / Q000032:analysis*; D013696:Temperature; D013997:Time Factors; D014783:Viscosity
chemical_list: D002511:Cephalosporins; D009883:Ophthalmic Solutions; D011725:Pyridines; D011142:Polyvinyl Alcohol; D002442:Ceftazidime; C023666:pyridine