Medetomidine
Encyclopedia
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.
, 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.
(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.
Analgesic
An analgesic is any member of the group of drugs used to relieve pain . The word analgesic derives from Greek an- and algos ....
often used as the hydrochloride
Hydrochloride
In chemistry, hydrochlorides are salts resulting, or regarded as resulting, from the reaction of hydrochloric acid with an organic base . This is also known as muriate, derived from hydrochloric acid's other name: muriatic acid....
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
Pfizer
Pfizer, Inc. is an American multinational pharmaceutical corporation. The company is based in New York City, New York with its research headquarters in Groton, Connecticut, United States...
Animal Health and by Novartis
Novartis
Novartis International AG is a multinational pharmaceutical company based in Basel, Switzerland, ranking number three in sales among the world-wide industry...
Animal Health in Canada under the product name Domitor. Other alpha-two agonists used in veterinary medicine include xylazine
Xylazine
Xylazine is a drug that is used for sedation, anesthesia, muscle relaxation, and analgesia in animals such as horses, cattle and other non-human mammals. An analogue of clonidine, it is an agonist at the α2 class of adrenergic receptor....
and detomidine
Detomidine
Detomidine is an imidazole derivative and α2-adrenergic agonist, used as a large animal sedative, primarily used in horses. It is usually available as the salt detomidine hydrochloride...
, but their use is less common in small animal surgery. The marketed product is a racemic mixture of 2 stereoisomers; dexmedetomidine
Dexmedetomidine
Dexmedetomidine is a sedative medication used by intensive care units and anesthetists. It is relatively unique in its ability to provide sedation without causing respiratory depression...
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.
In veterinary medicine
It is often used in combinations with opioids (butorphanolButorphanol
Butorphanol is a morphinan-type synthetic opioid analgesic developed by Bristol-Myers. Brand name Stadol was recently discontinued by the manufacturer. It is now only available in its generic formulations, manufactured by Novex, Mylan, Apotex and Ben Venue Laboratories. Butorphanol is most...
, buprenorphine
Buprenorphine
Buprenorphine is a semi-synthetic opioid that is used...
etc) as premedication (before a general anaesthetic
General anaesthetic
A general anaesthetic is a drug that brings about a reversible loss of consciousness. These drugs are generally administered by an anaesthesia provider to induce or maintain general anaesthesia to facilitate surgery...
) in healthy cats and dogs. It can be given by intramuscular injection
Intramuscular injection
Intramuscular injection is the injection of a substance directly into a muscle. In medicine, it is one of several alternative methods for the administration of medications . It is used for particular forms of medication that are administered in small amounts...
(IM), subcutaneous injection
Subcutaneous injection
A subcutaneous injection is administered as a bolus into the subcutis, the layer of skin directly below the dermis and epidermis, collectively referred to as the...
(SC) or intravenous injection (IV). When delivered intravenously, a significantly decreased dose is used. Some authors suggest a sublingual
Sublingual
Sublingual, literally 'under the tongue', from Latin, refers to the pharmacological route of administration by which drugs diffuse into the blood through tissues under the tongue...
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
Vasoconstriction
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...
and bradycardia
Bradycardia
Bradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart...
are noted. Often the dosage of induction agents (i.e. propofol
Propofol
Propofol is a short-acting, intravenously administered hypnotic agent. Its uses include the induction and maintenance of general anesthesia, sedation for mechanically ventilated adults, and procedural sedation. Propofol is also commonly used in veterinary medicine...
) may be drastically reduced, as may the volumes of anaesthetic gases (i.e. halothane
Halothane
Halothane is an inhalational general anesthetic. Its IUPAC name is 2-bromo-2-chloro-1,1,1-trifluoroethane. It is the only inhalational anesthetic agent containing a bromine atom; there are several other halogenated anesthesia agents which lack the bromine atom and do contain the fluorine and...
, isoflurane
Isoflurane
Isoflurane is a halogenated ether used for inhalational anesthesia. Together with enflurane and halothane, it replaced the flammable ethers used in the pioneer days of surgery. Its name comes from being a structural isomer of enflurane, hence they have the same empirical formula...
, sevoflurane
Sevoflurane
Sevoflurane , also called fluoromethyl hexafluoroisopropyl ether, is a sweet-smelling, nonflammable, highly fluorinated methyl isopropyl ether used for induction and maintenance of general anesthesia. Together with desflurane, it is replacing isoflurane and halothane in modern anesthesiology...
) used to maintain general anaesthesia.
It is sometimes used in combination with butorphanol and ketamine
Ketamine
Ketamine is a drug used in human and veterinary medicine. Its hydrochloride salt is sold as Ketanest, Ketaset, and Ketalar. Pharmacologically, ketamine is classified as an NMDA receptor antagonist...
(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
Morphine
Morphine is a potent opiate analgesic medication and is considered to be the prototypical opioid. It was first isolated in 1804 by Friedrich Sertürner, first distributed by same in 1817, and first commercially sold by Merck in 1827, which at the time was a single small chemists' shop. It was more...
(or methadone
Methadone
Methadone is a synthetic opioid, used medically as an analgesic and a maintenance anti-addictive for use in patients with opioid dependency. It was developed in Germany in 1937...
), lignocaine and ketamine in constant rate infusion analgesia in canines. It is often used in so called microdoses
Microdosing
Microdosing is a technique for studying the behaviour of drugs in humans through the administration of doses so low they are unlikely to produce whole-body effects, but high enough to allow the cellular response to be studied...
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 atipamezoleAtipamezole
Atipamezole is a synthetic alpha2-adrenergic antagonist, indicated for the reversal of the sedative and analgesic effects of dexmedetomidine and medetomidine in dogs. It has also been researched in humans as a potential anti-Parkinsonian drug.-External links:*...
(distributed as Antisedan by Pfizer). IV use of atipamezole is not licensed, IM is the preferred route. Yohimbine
Yohimbine
Yohimbine is an alkaloid with stimulant and aphrodisiac effects found naturally in Pausinystalia yohimbe . It is also found naturally in Rauwolfia serpentina , Alchornea floribunda , along with several other active alkaloids...
may also be used in an emergency situation, but is not licensed.