title: Alpha 2 adrenoceptor agonists in the horse--a review.
abstract: In recent years the usefulness of the alpha 2 adrenoceptor agonist drugs has been recognized in equine practice. Several agents have become available and are now licensed for use in a number of countries. The principle actions of all alpha 2 adrenoceptor agonists are similar, in that they produce a reduction in heart rate and alteration of heart rhythm, an initial hypertension followed by a prolonged hypotension, a decrease in the cardiac output and respiratory depression. For clinical purposes, these agents produce sedation and analgesia, they are useful for premedication and markedly potentiate the effects of other sedative/analgesic agents. Differences in receptor specificity between the alpha 2 adrenoceptor agonists results in the distinguishing characteristics of the individual agents, particularly with respect to their duration of action, sedative effect and analgesic properties; their cardiopulmonary effects are however similar, when equipotent sedative doses are administered. When used in combination with other agents, the alpha 2 adrenoceptor agonists all appear to act in a similar manner, with the greatest difference being related to their duration of action.
authors.affiliation: Department of Farm Animal and Equine Medicine and Surgery, Royal Veterinary College, University of London, North Mymms, Hatfield, UK.
authors.forename: G C
authors.initials: GC
authors.lastname: England
authors.forename: K W
authors.initials: KW
authors.lastname: Clarke
mesh_terms: D058647:Adrenergic alpha-2 Receptor Agonists; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D003000:Clonidine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006736:Horses / Q000502:physiology*; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D007093:Imidazoles / Q000494:pharmacology; D020926:Medetomidine; D012119:Respiration / Q000187:drug effects / Q000502:physiology; D014991:Xylazine / Q000494:pharmacology
chemical_list: D058647:Adrenergic alpha-2 Receptor Agonists; D000316:Adrenergic alpha-Agonists; D000700:Analgesics; D006993:Hypnotics and Sedatives; D007093:Imidazoles; D014991:Xylazine; C041255:detomidine; C076257:romifidine; D003000:Clonidine; D020926:Medetomidine