Medetomidine

Medetomidine

File:Medetomidine.svg
Systematic (IUPAC) name
(RS)-4-[1-(2,3-dimethylphenyl)ethyl]-3H-imidazole
Legal status
Legal status	Veterinary use only
Identifiers
CAS Number	86347-14-0
ATCvet code	QN05CM91 (WHO)
PubChem	CID 68602
Chemical data
Formula	C13H16N2
Molar mass	200.279 g/mol[[]]

Medetomidine is a synthetic drug used as both a surgical anesthetic and analgesic often used as the hydrochloride salt medetomidine hydrochloride. It is a crystalline white alpha-two adrenergic agonist that can be administered as an intravenous drug solution with sterile water. It is currently approved for dogs in the United States, and distributed in the United States by Pfizer Animal Health and by Novartis Animal Health in Canada under the product name Domitor. Other alpha-two agonists used in veterinary medicine include xylazine and detomidine, but their use is less common in small animal surgery. The marketed product is a racemic mixture of 2 stereoisomers; dexmedetomidine is the compound with more useful effects, and is now marketed as Dexdomitor.

The free base form of medetomidine is distributed by the Swedish company I-Tech AB under the product name Selektope for use as an antifouling substance in marine paints.

Uses

In veterinary medicine

It is often used in combinations with opioids (butorphanol, buprenorphine etc) as premedication (before a general anaesthetic) in healthy cats and dogs. It can be given by intramuscular injection (IM), subcutaneous injection (SC) or intravenous injection (IV). When delivered intravenously, a significantly decreased dose is used. Some authors suggest a sublingual route is also effective. It is not recommended for diabetics, it is contraindicated in patients with cardiac disease. Due to its potent sedative effects it is commonly used in more aggressive animals, where a drug/combination with a lesser effect (i.e. Acetylpromazine + an Opioid, an Opioid + a Benzodiapezine) would not allow the administration of the inductive agent without risk to the veterinarian. As such the use of alpha-two agonists is only recommended in healthy animals.

Following administration, marked peripheral vasoconstriction and bradycardia are noted. Often the dosage of induction agents (i.e. propofol) may be drastically reduced, as may the volumes of anaesthetic gases (i.e. halothane, isoflurane, sevoflurane) used to maintain general anaesthesia.

It is sometimes used in combination with butorphanol and ketamine (given IM) to produce general anaesthesia for short periods in healthy but fractious felines that will not allow an intravenous induction agent to be given. It provides a good degree of muscle relaxation, an important factor in Ketamine based anaethesia protocols.

Medetomidine has also been used in combination with morphine (or methadone), lignocaine and ketamine in constant rate infusion analgesia in canines. It is often used in so called microdoses for this analgesic effect.

It is thought that this family of drugs has a degree of analgesic action, though this is, in comparison to the sedative effect, minor.

In marine paint

Medetomidine can be used as an antifouling substance in marine paint. It is mainly effective against barnacles, but has also shown effect on other hard fouling like tubeworms. When the barnacle cyprid larva encounters a surface containing medetomidine the molecule enters the octopamine receptor in the larva. This makes the larva legs start kicking and it cannot settle to the painted surface. When the larva swims away from the surface, the effect disappears (reversible effect).The larva regain its function and can settle somewhere else.

Reversal of effects

Its effects can be reversed using atipamezole (distributed as Antisedan by Pfizer). IV use of atipamezole is not licensed, IM is the preferred route. Yohimbine may also be used in an emergency situation, but is not licensed.

See also

• Veterinary anesthesia

References

• Novartis Animal Health Canada[1]. 2003.
  Harari, J. Small Animal Surgery. Williams and Wilkins, Media, PA. 1996.

• Ulrika Lind, Magnus A Rosenblad, Linda Hasselberg Frank, Susanna Falkbring, Lars Brive, Jonne M Laurila, Katariina Pohjanoksa, Anne Vuorenpaa, Jyrki P Kukkonen, Lina Gunnarsson, Mika Scheinin, Lena G.E. Martensson Lindblad, and Anders Blomberg Octopamine receptors from the barnacle Balanus improvisus are activated by the alpha2-adrenoceptor agonist medetomidine (Fast Forward 20 May 2010) Molecular Pharmacology Aug 1, 2010; 78 (2)

• Dahlström M, Martensson LGE, Jonsson PR, Arnebrant T and Elwing H (2000) Surface active adrenoceptor compounds prevent the settlement of cyprid larvae of Balanus improvisus. Biofouling 16(2-4):191-203.de:Medetomidin