ABSTRACT
Methods were developed for the preparation and isolation of four oxidative degradation products of atorvastatin. ATV-FX1 was prepared in the alkaline acetonitrile solution of atorvastatin with the addition of hydrogen peroxide. The exposition of aqueous acetonitrile solution of atorvastatin to sunlight for several hours followed by the alkalization of the solution with potassium hydroxide to pH 8-9 gave ATV-FXA. By the acidification of the solution with phosphoric acid to pH 3 ATV-FXA1 and FXA2 were prepared. The isolation of oxidative degradation products was carried out on a reversed-phase chromatographic column Luna prep C18(2) 10 microm applying several separation steps. The liquid chromatography coupled with a mass spectrometer (LC-MS), high resolution MS (HR-MS), 1D and 2D NMR spectroscopy methods were applied for the structure elucidation. All degradants are due to the oxidation of the pyrrole ring. The most probable reaction mechanism is intermediate endoperoxide formation with subsequent rearrangement and nucleophilic attack by the 5-hydroxy group of the heptanoic fragment. ATV-FX1 is 4-[1b-(4-Fluoro-phenyl)-6-hydroxy-6-isopropyl-1a-phenyl-6a-phenylcarbamoyl-hexahydro-1,2-dioxa-5a-aza-cyclopropa[a]inden-3-yl]-3-(R)-hydroxy-butyric acid and has a molecular mass increased by two oxygen atoms with regard to atorvastatin. ATV-FXA is the regioisomeric compound, 4-[6-(4-Fluoro-phenyl)-6-hydroxy-1b-isopropyl-6a-phenyl-1a-phenylcarbamoyl-hexahydro-1,2-dioxa-5a-aza-cyclopropa[a]inden-3-yl]-3-(R)-hydroxy-butyric acid. Its descendants ATV-FXA1 and FXA2 appeared without the atorvastatin heptanoic fragment and are 3-(4-Fluoro-benzoyl)-2-isobutyryl-3-phenyl-oxirane-2-carboxylic acid phenylamide and 4-(4-Fluoro-phenyl)-2,4-dihydroxy-2-isopropyl-5-phenyl-3,6-dioxa-bicyclo[3.1.0]hexane-1-carboxylic acid phenylamide, respectively. Quantitative NMR spectroscopy was employed for the assay determination of isolated oxidative degradation products. The results obtained were used for the determination of the UV response factors relative to atorvastatin.
Subject(s)
Heptanoic Acids/analysis , Heptanoic Acids/chemistry , Oxygen/chemistry , Pyrroles/analysis , Pyrroles/chemistry , Acetonitriles/chemistry , Atorvastatin , Chemistry, Pharmaceutical/methods , Chromatography, High Pressure Liquid/methods , Chromatography, Liquid/methods , Drug Stability , Hydrogen Peroxide/chemistry , Hydrogen-Ion Concentration , Hydroxides/chemistry , Magnetic Resonance Spectroscopy , Mass Spectrometry/methods , Phosphoric Acids/chemistry , Potassium Compounds/chemistry , Ultraviolet RaysABSTRACT
The aim of the present study was to evaluate different pharmaceutically acceptable excipients as permeation enhancers for a low permeability drug, amoxicillin. As a model for the intestinal epithelium excised rat jejunum, mounted in side-by-side diffusion cells, was used. Amoxicillin was actively transported across the intestine in the serosal-to-mucosal direction, but only if glucose was present at the mucosal side. This effect of glucose was abolished by a multridrug resistance associated protein (MRP) inhibitor benzbromarone (0.04 mM), but not by verapamil (0.2 mM). Among the tested pharmaceutically acceptable excipients only sodium lauryl sulfate (0.2 mg/ml) increased the permeability of amoxicillin in the mucosal-to-serosal direction, which was accompanying with the abolishment of the secretory oriented transport of amoxicillin. Other excipients (0.07 2mg/ml Pluronic F68, 0.2 mg/ml Lutrol F127, 0.2 mg/ml Cremophor EL or 0.2 mg/ml Carbopol 934) have no influence on the permeability of amoxicillin. The effect of sodium lauryl sulfate on the active secretion of amoxicillin was mainly attributed to the reversible cellular ATP depletion. We concluded that sodium lauryl sulfate can be considered as a relatively safe permeation enhancer for amoxicillin in drug delivery systems intended to improve oral bioavailability of this drug.
