title: Absorption of morphine from a slow-release emulsion used to induce morphine dependence in rats.
abstract: This study was performed to measure absorption of morphine from the injection site following treatment of rats with slow-release emulsions formulated with morphine hydrochloride and morphine base. Samples of emulsion were collected from the injection site of halothane anesthetized animals at 24 and 48 h following emulsion treatment and concentrations of morphine remaining in the emulsion were analyzed using high-performance liquid chromatography (HPLC). In another group of morphine-treated rats, at times equivalent to collecting samples of emulsion, the intensity of naloxone-precipitated withdrawal behaviors was monitored. Both morphine base- and hydrochloride-containing emulsions induced a high degree of physical dependence in animals treated over 48 h. Release of morphine from emulsions containing morphine base was slower than that from the hydrochloride formulations. In the 24-h morphine base-treated animals, approximately 45% was absorbed from the injection site as opposed to 99% in the 24-h morphine hydrochloride-treated animals. These results suggest that morphine base containing emulsions provide a more sustained exposure to the opioid.
authors.affiliation: Department of Clinical and Experimental Pharmacology, The University of Adelaide, South Australia, Australia. asalem@medicine.adelaide.edu.au
authors.forename: A
authors.initials: A
authors.lastname: Salem
authors.forename: W
authors.initials: W
authors.lastname: Hope
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D003692:Delayed-Action Preparations / Q000493:pharmacokinetics*; D004655:Emulsions / Q000493:pharmacokinetics*; D005243:Feces; D005260:Female; D009020:Morphine / Q000493:pharmacokinetics*; D009021:Morphine Dependence / Q000175:diagnosis / Q000209:etiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D003692:Delayed-Action Preparations; D004655:Emulsions; D009020:Morphine