Dexmedetomidine has an eight times increased affinity for the α2-receptor
compared with clonidine and therefore produces less cardiovascular
instability at comparable doses.
Dexmedetomidine is principally used as a sedative in
mechanically ventilated patients in ICU. I t is particularly useful in those
patients with delirium.
Dexmedetomidine is the S -enantiomer of the veterinary anaesthetic medetomidine. It has highly selective activity at α2 adrenoceptors (1600 : 1 α2 : α1) and eight times more affinity than clonidine for this site. D exmedetomidine is licenced in the UK for i.v. sedation of adult patients in intensive care, although there is off-licence use, such as for procedural sedation during an awake craniotomy.
Dexmedetomidine is metabolised via hepatic glucuronidation, and clearance is reduced in patients with liver impairment. Very li??le unchanged drug reaches the urine, but 95% of degradation products are excreted this way (4% in faeces). There is a theoretical possibility of accumulation of metabolites in patients with renal failure, but toxicity has not been described because active metabolites of dexmedetomidine have not been identified at present.
Dexmedetomidine is freely soluble in water and has a pKa of 7.1. The pharmaceutical formulation is a clear, colourless preservative-free solution with a pH of 4.5–8. Protein binding of dexmedetomidine is 94%, with negligible displacement by drugs commonly used in anaesthetic and I CU practice. The elimination half-life is approximately 2h and the steady-state volume of distribution is 118 l. There are no significant differences in the pharmacokinetic profile in the elderly, but an enhanced clinical response is seen.
Veterinary Drugs and Treatments
In the USA, dexmedetomidine for dogs is approved for use as a sedative
and analgesic to facilitate clinical examinations, clinical procedures,
minor surgical procedures, and minor dental procedures, and
as a preanesthetic to general anesthesia.
In Europe, dexmedetomidine is additionally indicated for use in
cats similarly to dogs above, but when used as premed it is indicated
for use prior to ketamine general anesthesia.
