Products
Xylazine is commercially available as a solution for injection. It is approved exclusively as a veterinary drug in many countries and has been since 1970.
Structure and properties
Xylazine (C12H16N2S, Mr = 220.3 g/mol) is a thiazine derivative. It exists as a white crystalline powder that is readily soluble in water. In veterinary medicine xylazine hydrochloride is used. Xylazine has structural similarity to clonidine and comparable effects.
Effects
Xylazine (ATCvet QN05CM92) has depressant (sedative), sleep-inducing, analgesic, muscle relaxant, antihypertensive, and stimulant properties on uterine muscles. It has both central and peripheral effects. The effects of xylazine are dose and species dependent.
Mechanism of action
Xylazine is an α2-receptor agonist. Its effects are due to activation of α2-adrenergic receptors in the central and peripheral nervous systems. In the central nervous system, stimulation of these receptors results in sedation and pain relief. Inhibition of intraneuronal impulses in the spinal cord results in muscle relaxation.
Indications
For sedation, pain relief, and muscle relaxation in horses, cattle, zoo and wild animals, dogs, and cats. Xylazine is used for examinations and treatments such as castration, obstetrics, shoeing, x-rays, wound treatments, etc. The pain relief of Xylazine is not sufficient for surgical procedures, so other agents must be administered in addition. Furthermore, xylazine is used for pain relief in injuries and abdominal pain, as well as to calm unruly animals during loading and transport.
Dosage
According to the directions for use. Dosage is based on the desired effect. Xylazine is administered intravenously or intramuscularly, but may also be given epidurally into the spinal cord or subcutaneously. During the recovery period, animals should be in a quiet environment at room temperature and protected from sunlight.
Contraindications
Xylazine is contraindicated in hypersensitivity, volume deficiency, dehydration, urinary or digestive tract obstruction, cardiopulmonary disease, low blood pressure, diabetes mellitus, gastric distention, and gavage obstruction. Highly pregnant animals should not be given Xylazine because abortion or premature birth may occur due to contractions of the uterus. In sick or elderly animals, the dose must be decreased as they react more strongly to xylazine. In unruly, nervous, and agitated animals, the effect of xylazine is impaired. Therefore, after administration of xylazine, animals should be left alone until the onset of action. The user should never drive a car in case of accidental self-injection. Pregnant women should avoid handling xylazine, as accidental self-injection may cause a drop in fetal blood pressure and uterine contractions. For complete precautions, see the drug label.
Interactions
Combination of xylazine with other analgesics, opioids, barbiturates, chloral hydrate, ketamine, or isoflurane causes potentiation of effects and adverse reactions. Analeptics cause attenuation or shortening of prolonged, undesirable, or deep sedation.
Adverse effects
Possible adverse effects include a slow pulse, low blood pressure after an initial rise in blood pressure, cardiac arrhythmias, slowed breathing, hypothermia, increased urination, sweating, increased salivation, decrease in gastric and intestinal movements, decreased insulin secretion, increased blood glucose, and disturbances in motor coordination. In dogs and especially in cats, vomiting often occurs because the vomiting center is activated. This can be avoided by concomitant administration of metoclopramide or ketamine or by fasting. Deaths in dogs and cats have been reported. In dogs and ruminants, bloat may occur as a result of gas accumulation in the stomach or intestines. For this reason, these animals should be allowed to fast before administration of xylazine. In the event of an overdose, α2-receptor antagonists such as atipamezole, yohimbine, idazoxan, or tolazoline can be administered to reverse the effects of xylazine. Cold water showers may also help.
