title: Preliminary study on the effect of parenteral naloxone, alone and in association with calcium gluconate, on bone healing in an ovine "drill hole" model system.
abstract: BACKGROUND
  Several diseases affect bone healing and physiology. Many drugs that are commonly used in orthopaedics as "analgesics" or anti-inflammatory agents impair bone healing. Stressful conditions are associated with decreased serum osteocalcin concentration. High endorphin levels alter calcium metabolism, blocking the membrane channels by which calcium normally enters cells. The consequent decrease of intracellular calcium impairs the activities of calcium-related enzymes. Naloxone is a pure opioid antagonist. Morphine-induced osteocalcin inhibition was abolished when osteoblasts were incubated with naloxone. Naloxone restored the altered cellular and tissue physiology by removing beta-endorphins from specific receptors. However, this is only possible if the circulating Ca concentration is adequate. The aim of the present study was to evaluate the efficacy of parenteral naloxone administration in inducing fast mineralization and callus remodelling in a group of sheep with a standardised bone lesion.
  
  
  METHODS
  Twenty ewes were randomly assigned to 4 treatment groups. Group A acted as control, group B received a solution of calcium gluconate, group C a solution of naloxone, and group D a solution of calcium gluconate and naloxone. A transverse hole was drilled in the left metacarpus, including both cortices, then parenteral treatment was administered intramuscularly, daily for four weeks. Healing was evaluated by weekly radiographic examination for eight weeks. For quantitative evaluation, the ratio of the radiographic bone density between the drill area and the adjacent cortical bone was calculated. After eight weeks the sheep were slaughtered and a sample of bone was collected for histopathology
  
  
  RESULTS
  Group D showed a higher radiographic ratio than the other groups. Sheep not treated with naloxone showed a persistently lower ratio in the lateral than the medial cortex (P < 0.01). Histopathology of bone samples showed more caverns and fewer osteoblasts in group D than in the other groups (P </= 0.001).
  
  
  CONCLUSIONS
  A low-dose parenteral regimen of naloxone enhances mineralization and remodelling of the callus in healing cortical defects in sheep, especially if associated with calcium gluconate.
authors.affiliation: Department of Veterinary Clinical Sciences, University of Teramo, Italy. lpetrizzi@unite.it
authors.forename: Lucio
authors.initials: L
authors.lastname: Petrizzi
authors.forename: Massimo
authors.initials: M
authors.lastname: Mariscoli
authors.forename: Luca
authors.initials: L
authors.lastname: Valbonetti
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Varasano
authors.forename: Jens D
authors.initials: JD
authors.lastname: Langhoff
authors.forename: Brigitte
authors.initials: B
authors.lastname: Von Rechenberg
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000293:injuries; D002125:Calcium Gluconate / Q000494:pharmacology*; D004195:Disease Models, Animal; D004359:Drug Therapy, Combination; D005260:Female; D017102:Fracture Healing / Q000187:drug effects*; D007273:Injections, Intramuscular; D008663:Metacarpus / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000293:injuries; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D010012:Osteogenesis / Q000187:drug effects; D011859:Radiography; D012756:Sheep
chemical_list: D009292:Narcotic Antagonists; D009270:Naloxone; D002125:Calcium Gluconate