Target species
Nerfasin 20 mg/ml Solution for Injection for Cattle, Horses, Dogs and Cats:
Cattle, horses, dogs and cats.
Nerfasin 100 mg/ml Solution for Injection for Cattle and Horses:
Cattle (≥ 200 kg) and horses.
Indications for use
Sedation. Premedication in combination with an anaesthetic.
Contraindications
Do not use in case of hypersensitivity to the active substance or to any of the excipients.
Do not use in animals with gastrointestinal obstruction as the muscle relaxant properties of the drug appear to accentuate the effects of the obstruction and because of possible vomiting.
Do not use in animals with severe renal or hepatic impairment, respiratory dysfunction, cardiac abnormalities, hypotension and/or shock.
Do not use in diabetic animals.
Do not use in animals with a history of seizures.
Do not use in calves younger than 1 week of age, foals younger than 2 weeks or in puppies and kittens younger than 6 weeks.
Do not use in cattle weighing less than 200 kg body weight. Do not use in foals younger than 2 weeks.
Do not use during the last stage of pregnancy (danger of premature birth), except at parturition (see Use during pregnancy and lactation).
Special warnings for each target species
Horses:
Xylazine inhibits the normal intestinal motility. Therefore, it should only be used in horses with colic, that are not responsive to analgesics. The use of xylazine should be avoided in horses with caecal malfunction.
After treatment of horses with xylazine, the animals are reluctant to walk, so whenever possible the drug should be administered in the place where the treatment/investigation is going to take place.
Caution should be taken in the administration of the product to horses susceptible to laminitis.
Horses with airway disease or malfunction may develop life-threatening dyspnoea.
The dose should be kept as low as possible.
The association with other pre-anaesthetic agents or anaesthetic agents should be the subject of a benefit/risk assessment. This assessment should consider the composition of the products, their dose and the nature of the surgery. Recommended dosages are likely to vary according to the choice of the anaesthetic association.
Cats and dogs:
Xylazine inhibits the normal intestinal motility. This may make xylazine sedation undesirable for upper gastro-intestinal radiographs, because it promotes filling of the stomach with gas and makes interpretation less certain.
Brachycephalic dogs with air way disease or malfunction may develop life-threatening dyspnoea.
The association with other pre-anaesthetic agents or anaesthetic agents should be the subject of a benefit/risk assessment. This assessment should consider the composition of the products, their dose and the nature of the surgery. Recommended dosages are likely to vary according to the choice of the anaesthetic association.
Cattle:
Ruminants are highly susceptible to the effects of xylazine. Normally cattle remain standing at the lower doses, but some animals may lie down. At the highest recommended doses most animals will lie down and some animals may lapse in lateral recumbency.
Reticulo-ruminal motor functions are depressed after injection of xylazine. This may result in bloat. It is advisable to withhold feed and water for several hours before administration of xylazine.
In cattle the ability to eructate, cough and swallow is retained but reduced during the period of sedation, therefore cattle must be closely watched during the recovery period: the animals should be maintained in sternal recumbency.
In cattle life threatening effects may occur after intramuscular doses above 0.5 mg/kg body weight (respiratory and circulatory failure). Therefore very precise dosing is required.
This product should only be used in cattle weighing 200 kg or more. Since it is highly concentrated, a slight deviation from the actual volume to be injected may cause serious adverse reactions. In case cattle weighing less than 200 kg need to be treated, xylazine with a lower strength should be used (e.g. 20 mg/ml).
The association with other pre-anaesthetic agents or anaesthetic agents should be the subject of a benefit/risk assessment. This assessment should consider the composition of the products, their dose and the nature of the surgery. Recommended dosages are likely to vary according to the choice of the anaesthetic association.
Special precautions for use in animals
Keep the animals calm, because they may respond to external stimuli.
Avoid intra-arterial administration.
Tympany may occasionally occur in recumbent cattle and can be avoided by maintaining the animal in sternal recumbency.
To avoid aspiration of saliva or food, lower the animal’s head and neck. Fast the animals before use of the product.
Older and exhausted animals are more sensitive to xylazine, whilst nervous or highly excitable animals may require a relatively high dose.
In case of dehydration, xylazine should be used cautiously.
Emesis is generally seen within 3-5 minutes after xylazine administration in cats and dogs. It is advisable to fast dogs and cats for 12 hours prior to surgery; they may have free access to drinking water.
Pre-medication with atropine in cats and dogs may reduce salivation and bradycardia effects
Do not exceed the recommended dosage.
Following administration animals should be allowed to rest quietly until the full effect has been reached.
It is advised to cool animals when the ambient temperature is above 25°C and to keep animals warm at low temperatures.
For painful procedures, xylazine should always be used in combination with local or general anaesthesia.
Xylazine produces a certain degree of ataxia; therefore, xylazine must be used cautiously in procedures involving the distal extremities and in standing castrations in the horse.
Treated animals should be monitored until the effect has faded totally (e.g. cardiac and respiratory function, also in the post-operative phase) and should be segregated to avoid bullying.
For use in young animals, see the age restriction mentioned in Contraindications. If the product is intended to be used in young animals below these age-limits, a benefit/risk assessment should be made by the veterinarian.
Special precautions to be taken by the person administering the veterinary medicinal product to animals
Care should be taken to avoid accidental self-injection. In case of accidental oral intake or self-injection, seek medical advice immediately and show the package leaflet to the physician but DO NOT DRIVE as sedation and changes in blood pressure may occur.
Avoid skin, eye or mucosal contact.
Wash the exposed skin immediately after exposure with large amounts of water.
Remove contaminated clothes that are in direct contact with skin.
In the case of accidental contact of the product with eyes, rinse abundantly with fresh water. If symptoms occur, seek the advice of a physician.
If pregnant women handle the product, special caution should be observed not to self-inject as uterine contractions and decreased foetal blood pressure may occur after accidental systemic exposure.
Advice to doctors:
Xylazine is an α2-adrenoreceptor agonist, symptoms after absorption may involve clinical effects including dose-dependent sedation, respiratory depression, bradycardia, hypotension, a dry mouth and hyperglycaemia. Ventricular arrhythmias have also been reported. Respiratory and haemodynamic symptoms should be treated symptomatically.
Adverse reactions
In general, side effects, typical for an α2-adrenergic agonist, like bradycardia, reversible arrhythmia and hypotension can occur. Thermoregulation can be influenced and consequently body temperature can decrease or increase dependant on the ambient temperature. Depression of respiration and/or respiratory arrest can occur, especially in cats.
Cats and dogs:
Cats and dogs frequently vomit during the onset of the xylazine-induced sedation, especially when the animals have just been fed.
Animals may show profound salivation following an injection with xylazine.
Other adverse effects for dogs and cats include: muscle tremors, bradycardia with AV-block, hypotension, reduced respiratory rate, movement in response to strong auditory stimuli, hyperglycaemia and increased urination in cats.
In cats xylazine causes uterine contractions and it may induce premature parturition.
In dogs, adverse effects are generally more pronounced after subcutaneous administration compared to intramuscular and the effect (efficacy) can be less predictable.
In susceptible dog breeds with a large chest (Great Dane, Irish Setter) rare cases of bloating have been reported.
In anaesthetized animals, mainly during and after the recovery period, in very rare cases, cardio-respiratory disturbances (cardiac arrest, dyspnea, bradypnea, pulmonary edema, hypotension) and neurological signs (seizures, prostration, pupillary disorders, tremors) were observed.
Cattle:
In cattle xylazine may induce premature parturition, and it also reduces implantation of the ovum.
Cattle, which have received high doses of xylazine sometimes suffer from loose faeces for 24 hours afterwards.
Other adverse reactions include snoring, profound salivation, ruminal atony, atony of the tongue, regurgitation, bloating, nasal stridor, hypothermia, bradycardia, increased urination and reversible prolapse of the penis.
In cattle, adverse effects are generally more pronounced after intramuscular administration compared to intravenous.
Horses:
Horses often sweat as the effects of the sedation are wearing off.
Severe bradycardia and reduced respiratory rate have been reported especially in horses.
Following administration to horses, a transient rise followed by a fall in blood pressure usually occurs.
More frequent urination has been reported.
Muscle tremors and movement in response to sharp auditory or physical stimuli are possible. Although rare, violent reactions have been reported in horses following the administration of xylazine.
Ataxia and reversible prolapse of the penis may occur.
In very rare cases xylazine may induce mild colic as the gut motility is depressed temporarily. As a preventive measure the horse should receive no feed after sedation until the effect has faded completely.
The frequency of adverse reactions is defined using the following convention:
- very common (more than 1 in 10 animals displaying adverse reaction(s) during the course of one treatment)
- common (more than 1 but less than 10 animals in 100 animals)
- uncommon (more than 1 but less than 10 animals in 1,000 animals )
- rare (more than 1 but less than 10 animals in 10,000 animals)
- very rare (less than 1 animal in 10,000 animals, including isolated reports).
Use during pregnancy and lactation
Although laboratory studies in rats have not shown any evidence of teratogenic or foetotoxic effects the use of the product during the first two trimesters of pregnancy should only be made according to the benefit/risk assessment by the responsible veterinarian.
Do not use in the later stages of pregnancy (particularly in cattle and cats) except at parturition, because xylazine causes uterine contractions and it may induce premature labour.
Do not use in cattle receiving ovum transplants as the increased uterine tone may reduce the chance of implantation of the ovum.
Interactions
Other CNS depressant agents (barbiturates, narcotics, anaesthetics, tranquillizers, etc.) may cause additive CNS depression if used with xylazine. Dosages of these agents may need to be reduced. Xylazine should therefore be used cautiously in combination with neuroleptics or tranquillizers.
Xylazine should not be used in combination with sympathomimetic drugs such as epinephrine as ventricular arrhythmia may follow.
The concurrent intravenous use of potentiated sulphonamides with alpha-2 agonists has been reported to cause cardiac arrhythmias which may be fatal. Whilst no such effects have been reported with this product, it is recommended that intravenous administration of Trimethoprim/Su
