title: pH stability of ophthalmic solutions.
abstract: BACKGROUND
  In this study, we evaluated the pH value of 17 ophthalmic solutions, and we investigated whether the pH of these solutions changed over time after the bottle was opened.
  
  
  METHODS
  Fifteen bottles of each type of solution were chosen at random from different production lots. A 0.05-ml increment was taken from each bottle and was measured daily using a micropH 2002 Crison pH-meter over a period of 30 days.
  
  
  RESULTS
  The results revealed differences between the pH values of the solutions; nine solutions presented pH values within ocular comfort range and eight solutions presented pH values between 3.5 and 6.4. Ten solutions presented nonstatistically significant variations over time (p > 0.01) and seven solutions presented isolated but statistically significant variations.
  
  
  CONCLUSIONS
  We may assume that the nine solutions with pH values within the ocular comfort range will not produce initial discomfort. The solutions with acid pH values will produce initial discomfort. The solutions with nonstatistically significant pH variations over 30 days in relation to their initial pH values presented great stability.
authors.affiliation: Ocular Surface, Cornea, and Contact Lenses Research Group, Department d'Optica, Universitat de València, València, Spain.
authors.forename: Monica
authors.initials: M
authors.lastname: Garcia-Valldecabres
authors.forename: Antonio
authors.initials: A
authors.lastname: López-Alemany
authors.forename: Miguel F
authors.initials: MF
authors.lastname: Refojo
mesh_terms: D004355:Drug Stability; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009883:Ophthalmic Solutions
chemical_list: D009883:Ophthalmic Solutions