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Dr. T.V.Jayamohanan, Abudhabi, UAE,   19 - Sep - 2016
Medetomidine as an alternative to Xylazine

Clinician’s Corner

Medetomidine as an alternative to Xylazine

 Dr. T.V.Jayamohanan, Abudhabi, UAE

  tvjmohanan@yahoo.co.in

Medetomidine is an alpha 2-adrenoceptor agonist used to achieve sedation and analgesiain animals especially dogs and cats .It resembles xylazine in its action and has wide margin of safety. It produces vagal effects but degree of hypertension produced is very less. It is a potent alpha 2-adrenoceptor agonist and stimulates receptors centrally to produce dose-dependent sedation and analgesia and receptors centrally and peripherally to cause marked bradycardia and decrease the cardiac output. Other actions that follow medetomidine use are slowing of gastrointestinal motility, hypothermia, changes to endocrine function and, occasionally, vomiting and muscle twitching. After intramuscular injection, the effects of are seen within 10 to 15 minutes and  after intravenous injection, within 5 minutes. The analgesia lasts for 15 to 30 minutes but sedation can last 1 to 2 hours. Complete recovery can take 2 to 4 hours. Due to its anaesthetic sparing effect, dose of intravenous and inhalant general anaesthetics can be considerably reduced.

Vomiting usually occurs within the first 3 to 5 minutes after IM injection. Care should be taken in animals with hepatic, renal and cardiovascular diseases or in poor general health. Medetomidine should not be used in the last trimester of pregnancy since it can induce premature labor. It is also better avoided in animals less than 12 weeks of age. The actions can be rapidly reversed with the specific alpha 2-adrenoceptor antagonist, atipamezole. In dogs and cats medetomidine can be used either alone or in combination with butorphenol for restraint, sedation and analgesia associated with clinical procedures, minor surgery and as a premedicant before general anaesthesia using injectable anaesthetic (ketamine) and inhalant anaesthetic (isofluorane).

              The drug is marketed as Domitor( 10ml vial containing 1mg medetomidine hydrochloride per ml). Butorphanol is a centrally acting analgesic which helps to enhance sedative action of medetomidine and is marketed as Torbugesic( 10ml vial containing 10mg per ml of butorphenol tartrate). Atipemazole is marketed as Antisedan( 10ml vial containing 5mg atipemazole hydrochloride per ml).

Animal

Dose of medetomidine

(µg/kg)

Effect

       Dog

10-30

Slight sedation

30-80

Moderate to deep sedation and analgesia

10-20

Pre-anaesthesia

      Cats

50-100

Moderate sedation

100-150

Deep sedation

Intramuscular injection of a combination of 0.1 ml each of Domitor ,Torbugesic and Ketamine ( Ketaset or Ketalarcontaining 100mg ketamine hydrochloride per ml) is very effective to restrain a cat weighing 2kg for minor surgical procedures.The effect can be reversed by an equal volume of Antisedan. Recommended doses of medetomidine in cattle and pigs are 20-50 µg and 80 µg per kg respectively.