title: Analgesic effects of intraneural injection of ethyl alcohol or formaldehyde in the palmar digital nerves of horses.
abstract: OBJECTIVE
  To determine analgesic effects of intraneural injection of ethyl alcohol or formaldehyde in the palmar digital nerves of horses.
  
  
  METHODS
  6 horses.
  
  
  METHODS
  Ethyl alcohol was injected in the medial palmar digital nerve of 1 forelimb, and formaldehyde was injected in the contralateral nerve. The lateral palmar digital nerve in 1 forelimb was surgically exposed, but not injected, and the contralateral lateral palmar digital nerve was not treated. For each heel, severity of lameness in response to experimentally induced heel pain (lameness score and peak vertical force), thermal reaction time, and heel skin sensitivity scores were recorded. Heel pain was experimentally induced by advancing a threaded bolt through a custom-made horseshoe to apply pressure to the palmar horned aspect of the hoof. Horses were followed up for 112 days, when a subset of nerves was sampled for histologic analysis.
  
  
  RESULTS
  Alcohol and formaldehyde significantly reduced all measures of heel pain, and analgesia was evident over the 112 days of the study. Pastern circumference was significantly greater for formaldehyde-treated than for alcohol-treated limbs. Histologic evaluation showed preservation of nerve fiber alignment with an intact epineurium, loss of axons, axon degeneration, fibrosis, and inflammation in alcohol-treated and formaldehyde-treated nerves.
  
  
  CONCLUSIONS
  Results suggested that intraneural injection of either ethyl alcohol or formaldehyde in the palmar digital nerves of horses resulted in substantial, but partial, heel analgesia that persisted for at least 112 days. No advantage of formaldehyde over alcohol was found, and formaldehyde resulted in greater soft tissue inflammation.
authors.affiliation: Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210.
authors.forename: Christine P
authors.initials: CP
authors.lastname: Schneider
authors.forename: Akikazu
authors.initials: A
authors.lastname: Ishihara
authors.forename: Todd P
authors.initials: TP
authors.lastname: Adams
authors.forename: Lisa J
authors.initials: LJ
authors.lastname: Zekas
authors.forename: Michael
authors.initials: M
authors.lastname: Oglesbee
authors.forename: Alicia L
authors.initials: AL
authors.lastname: Bertone
mesh_terms: D000698:Analgesia / Q000662:veterinary; D000700:Analgesics / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D000431:Ethanol / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D005552:Forelimb; D005557:Formaldehyde / Q000008:administration & dosage / Q000494:pharmacology*; D006724:Hoof and Claw / Q000187:drug effects / Q000294:innervation*; D006736:Horses / Q000502:physiology*; D007267:Injections / Q000662:veterinary; D010146:Pain / Q000662:veterinary*
chemical_list: D000700:Analgesics; D005557:Formaldehyde; D000431:Ethanol