ATC vet code:
QN05CM91.
Pharmacotherapeutic group: sedative and analgesic.
Pharmacodynamics
The active ingredient of Domitor is medetomidine. Its chemical structure is 4 [1 (2,3 dimethylfenyl)ethyl] lH imidazole hydrochloride. Medetomidine is an alpha-2 adrenergic agonist with central and peripheral effects inhibiting the transmission of noradrenaline mediated nerve impulses by activating pre-and post-synaptic alpha-2 adrenoceptors. In the animal, the level of consciousness is lowered and the pain threshold is raised. The action of medetomidine is dose dependent: small doses cause mild sedation and analgesia, while larger doses produce high levels of sedation and analgesia.
Medetomidine lowers the heart rate and initially elevates the blood pressure; blood pressure returns to baseline or slightly below baseline over fifteen minutes The cardiovascular changes observed are either centrally mediated (bradycardia, hypotension) or due to direct effects on alpha-2 receptors (vasoconstriction, increased systemic vascular resistance).
The vasoconstriction may turn the mucous membranes pale or slightly bluish. Dogs may develop benign conductivity disturbances (first or second degree AV block). The respiratory rate is lowered. Local muscular twitching may occur in a few individuals. Blood glucose levels are elevated in both animal species. Body temperature decreases.
Pharmacokinetics
Medetomidine is rapidly absorbed after intramuscular injection; the tmax varies from 15 to 30 min. Medetomidine is also rapidly distributed in the organism. The Vd varies between 2.8 and 3.6 L/kg. Protein binding is 85 to 90%. Medetomidine is oxidised in the liver and a small proportion is methylated in the kidneys. Most metabolites are excreted in the urine. The T½ is 1-2 hours.