title: Microenvironmental pH measurement during sodium naproxenate dissolution in acidic medium by UV/vis imaging.
abstract: Variable dissolution from sodium salts of drugs containing a carboxylic acid group after passing the acidic environment of the stomach may affect oral bioavailability. The aim of the present proof of concept study was to investigate pH effects in relation to the dissolution of sodium naproxenate in 0.01M hydrochloric acid. For this purpose a UV/vis imaging-based approach capable of measuring microenvironmental pH in the vicinity of the solid drug compact as well as monitoring drug dissolution was developed. Using a pH indicating dye real-time spatially resolved measurement of pH was achieved. Sodium naproxenate, can significantly alter the local pH of the dissolution medium, is eventually neutralized and precipitates as the acidic species naproxen. The developed approach is considered useful for detailed studies of pH dependent dissolution phenomena in dissolution testing.
authors.affiliation: Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark. Electronic address: jesper.ostergaard@sund.ku.dk.
authors.forename: Jesper
authors.initials: J
authors.lastname: Østergaard
authors.affiliation: Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark. Electronic address: henrik.jensen@sund.ku.dk.
authors.forename: Henrik
authors.initials: H
authors.lastname: Jensen
authors.affiliation: Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark. Electronic address: susan.larsen@sund.ku.dk.
authors.forename: Susan W
authors.initials: SW
authors.lastname: Larsen
authors.affiliation: Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark. Electronic address: claus.larsen@sund.ku.dk.
authors.forename: Claus
authors.initials: C
authors.lastname: Larsen
authors.affiliation: DissoFX, 25 Cooper Street, Machias, ME 04654, USA. Electronic address: jhlenke@gmail.com.
authors.forename: Jim
authors.initials: J
authors.lastname: Lenke
mesh_terms: D011232:Chemical Precipitation; D002626:Chemistry, Pharmaceutical; D005456:Fluorescent Dyes / Q000737:chemistry; D006851:Hydrochloric Acid / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009288:Naproxen / Q000737:chemistry*; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet; D013678:Technology, Pharmaceutical / Q000379:methods*; D013944:Thymolphthalein / Q000031:analogs & derivatives / Q000737:chemistry
chemical_list: D005456:Fluorescent Dyes; D009288:Naproxen; C013713:thymol blue; D006851:Hydrochloric Acid; D013944:Thymolphthalein
keywords: Dissolution; Microenvironment pH; Precipitation; UV imaging; pH dependent dissolution