title: Identification of a yellow impurity in aged samples of aqueous butamben suspension: evidence for the oxidative degradation of poly(ethylene glycol).
abstract: Butamben (butyl p-aminobenzoate) has been formulated to provide long-acting treatment for chronic pain. The suspension, which contains poly(ethylene glycol) and polysorbate 80, was found to yellow under ambient conditions if not adequately protected from oxygen. The impurity responsible for the color was isolated and identified on the basis of nuclear magnetic resonance spectroscopy and mass spectrometry. The compound is an oxalamidine, which is formally the condensation product of oxalic acid with four equivalents of butamben, and may be formed by the reaction of butamben with an oxidation product of poly(ethylene glycol).
authors.affiliation: Hospital Products Division, Abbott Laboratories, Department 97D, Building AP4, 100 Abbott Park Road, Abbott Park, Illinois 60064-6076, USA. eric.ginsburg@abbott.com
authors.forename: E J
authors.initials: EJ
authors.lastname: Ginsburg
authors.forename: D A
authors.initials: DA
authors.lastname: Stephens
authors.forename: P R
authors.initials: PR
authors.lastname: West
authors.forename: A M
authors.initials: AM
authors.lastname: Buko
authors.forename: D H
authors.initials: DH
authors.lastname: Robinson
authors.forename: L C
authors.initials: LC
authors.lastname: Li
authors.forename: A R
authors.initials: AR
authors.lastname: Bommireddi
mesh_terms: D001566:Benzocaine / Q000031:analogs & derivatives* / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D011092:Polyethylene Glycols / Q000737:chemistry*; D016339:Spectrometry, Mass, Fast Atom Bombardment; D014867:Water
chemical_list: D014867:Water; D011092:Polyethylene Glycols; C004605:butamben; D001566:Benzocaine