title: Concentration of latanoprost ophthalmic solution after 4 to 6 weeks' use in an eye clinic setting.
abstract: OBJECTIVE
  To determine the concentration of latanoprost in bottles of latanoprost ophthalmic solution 0.005% after 4 or 6 weeks of use in patients in an eye clinic setting.
  
  
  METHODS
  Patients treated with latanoprost for open-angle glaucoma or ocular hypertension were randomly assigned to refill their prescriptions either at the Doheny Eye Institute clinic or a local pharmacy. Patients who used latanoprost binocularly were asked to return bottles to the clinic after 4 weeks of use and nonrefrigerated storage, and those who used latanoprost monocularly were asked to return used bottles after 6 weeks. Patients were then interviewed to determine bottle storage information and doses missed. Latanoprost concentration in residual solution was analyzed in a masked fashion, by reversed-phase high-performance liquid chromatography (HPLC).
  
  
  RESULTS
  In all, 110 patients were enrolled and 89 returned their bottles. Sixty-nine bottles had sufficient residual volume to conduct HPLC analysis. All patients reported that bottles were stored at room temperature (average high from 70-95 degrees F during the daytime). The mean +/- SD latanoprost concentration measured in the residual solutions was 48.31 +/- 2.31 microg/mL. Ninety-four percent of the bottles had concentrations within 90% to 110% of the labeled amount. No difference in latanoprost concentrations was found between the bottles used for 4 weeks versus those used for 6 weeks.
  
  
  CONCLUSIONS
  In an eye clinic setting, latanoprost ophthalmic solution 0.005% remains stable after 4 or 6 weeks of patient use from the same bottle when stored at room temperature.
authors.affiliation: Department of Ophthalmology, Keck School of Medicine, Los Angeles, University of Southern California, California 90033, USA. rvarma@usc.edu
authors.forename: Rohit
authors.initials: R
authors.lastname: Varma
authors.forename: Jonathan
authors.initials: J
authors.lastname: Winarko
authors.forename: Tien
authors.initials: T
authors.lastname: Kiat-Winarko
authors.forename: Benjamin
authors.initials: B
authors.lastname: Winarko
mesh_terms: D000368:Aged; D000959:Antihypertensive Agents / Q000032:analysis* / Q000627:therapeutic use; D002851:Chromatography, High Pressure Liquid; D004355:Drug Stability; D004356:Drug Storage; D005260:Female; D005901:Glaucoma / Q000188:drug therapy; D006801:Humans; D000077338:Latanoprost; D008297:Male; D009883:Ophthalmic Solutions / Q000032:analysis / Q000627:therapeutic use; D004364:Pharmaceutical Preparations / Q000032:analysis; D011461:Prostaglandins F, Synthetic / Q000032:analysis* / Q000627:therapeutic use; D013696:Temperature; D013997:Time Factors
chemical_list: D000959:Antihypertensive Agents; D009883:Ophthalmic Solutions; D004364:Pharmaceutical Preparations; D011461:Prostaglandins F, Synthetic; D000077338:Latanoprost