Dexmedetomidine

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Sections available in full article Name, Class of drug, Description, Uses, Administration, Do not mix with, Routes of administration, Dosage, Timing of administration, Pharmocokinetics, Normal, Physiological, variations, Pathological variations, Precautions, Contra-indications, Use with care, Interactions, Adverse reactions, Sources, Publications, Organization(s),
Contributors Dr Linda Horspool BVMS PhD DECVPT MRCVS
Synonyms Dextrorotatory enantiomer of medetomidine; S-enantiomer of medetomidine

Name

  • Dexmedetomidine hydrochloride.

Class of drug

  • Alpha2 adrenergic agonist.

Uses

Action

  • Potent and selective alpha2-adrenoceptor agonist that inhibits the release of noradrenaline from noradrenergic neurons.
    • Produces sedation and analgesia - duration and depth are dose-dependent.
    • Reduced heart rate and temporary atrioventricular (AV) block can be seen.
    • Blood pressure decreases to normal or below normal levels after an initial increase.
    • Respiration rate can occasionally decrease.
    • Other alpha2-adrenoceptor mediated effects include:
      • Piloerection.
      • Depression of motor and secretory functions of the gastrointestinal tract.
      • Diuresis.
      • Hyperglycemia.
      • Slight decrease in body temperature.
  • Sympathetic neurotransmission is prevented and the level of consciousness decreases. At maximal effect, the animal is relaxed, recumbent and does not respond to external stimuli.

Restraint, sedation and analgesia

  • Used for:
    • Non-invasive, mildly to moderately painful, procedures and examinations which require restraint, sedation and analgesia.
    • Deep sedation and analgesia in combination with butorphanol for medical and minor surgical procedures.
    • Premedication Anesthetic premedication: overview before induction and maintenance of general anesthesia.
  • Concomitant administration with butorphanol Butorphanol tartrate produces sedation and analgesia starting around 15 minutes post-administration, peaking after 30 minutes and lasting up to 90 minutes (analgesia) to 2 hours (sedation). Spontaneous recovery occurs within 3 hours.

Adverse reactions

Other reported reactions

  • Corneal opacities may occur during sedation (particularly in cats).
    • Protect eyes of dogs using a suitable eye lubricant.
  • Cardiovascular system:
    • Hypotension (following hypertension).
    • Bradycardia.
    • Pale or cyanotic mucous membranes (peripheral vasoconstriction).
    • Brady- (such as profound sinus bradycardia, sinus arrest and 1st or 2nd degree AV block) or tachyarrhythmias (such as atrial, supraventricular and ventricular premature complexes). Rarely supraventricular and ventricular premature complexes, sinus pause and 3rd degree AV block.
  • Respiratory system:
    • Bradypnea - reduced respiratory rate - or tachypnea.
    • Intermittent respiratory patterns - several rapid breaths following periods of apnea).
    • Hypoventilation.
    • Apnea - often for 20-30 seconds.
    • Hypoxemia.
    • Rarely pulmonary edema.
  • Body temperature decrease - hypothermia.
  • Musculoskeletal system: muscle tremors, twitching or paddling.
  • Gastrointestinal system:
    • Retching - 5-10 minutes after administration.
    • Vomiting - 5-10 minutes after administration and in some dogs at the time of recovery.

Treatment

  • Suspected side effects, as well as sedation and analgesia, can be reversed using an alpha adrenergic antagonist, eg atipamezole (Antisedan, Pfizer).

Antidote for overdose

  • In cases of overdosage, or potentially life-threatening side effects, atipamezole (5 mg/ml) should be administered.
    • To dogs, at a volume equal to the dexmedetomidine dose (10 times the dose).
  • Atipamezole rapidly reverses the effects of dexmedetomidine and thus shortens the recovery period - dogs are normally awake and standing within 15 minutes.

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