title: Effect of ionic and non-ionic polymer on the pH of lidocaine hydrochloride preparation assessed below and over human skin surface temperature.
abstract: Lidocaine is widely accepted local anesthetic, which is applied in the form of freely soluble hydrochloride salt. In this study we evaluated the pH of respective solutions of lidocaine hydrochloride with ionic polymer--polyacrylic acid or non-ionic polymer--methylcellulose, and compared to physiological skin conditions in the range between 22 degrees C and 41 degrees C. In microscopic observation of lidocaine hydrochloride preparations with polyacrylic acid the micro-sedimentation was revealed, however obtained mixture was opalescent, and homogenously dispersed in aqueous environment. The pH was maintained on the level not higher then 4,0 in the period of 12 hours for polyacrylic acid formulation, whereas in the case of preparation with methylcellulose, the pH increased from acceptable pH of ca. 4,5 to the level of above 6,0. The polyacrylic acid derivatives should be further studied as vehicles forming preparations with stable pH value during application on the skin, with more specific methods including pH microelectrodes, sufficient for assessments in small quantities of liquids of skin surface.
authors.affiliation: University of Maribor, Department for Textile Materials and Design, Laboratory for Chemistry Dyes and Polymers, Slovenia. witold@ktpl.am.wroc.pl
authors.forename: Witold
authors.initials: W
authors.lastname: Musial
authors.forename: Vanja
authors.initials: V
authors.lastname: Kokol
authors.forename: Bojana
authors.initials: B
authors.lastname: Voncina
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000287:Administration, Topical; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000737:chemistry*; D001831:Body Temperature; D002626:Chemistry, Pharmaceutical; D006801:Humans; D006863:Hydrogen-Ion Concentration; D052578:Ionic Liquids / Q000737:chemistry*; D008012:Lidocaine / Q000008:administration & dosage / Q000737:chemistry*; D012867:Skin / Q000737:chemistry; D012996:Solutions / Q000737:chemistry
chemical_list: D000180:Acrylic Resins; D000779:Anesthetics, Local; D052578:Ionic Liquids; D012996:Solutions; C006903:carbopol 940; D008012:Lidocaine