POM-V
Prescription Required
Nerfasin 100 mg/ml, Solution for Injection for Cattle and Horses
Active ingredient: Xylazine
Form
Injection
Species
Cattle
Horses
Manufacturer
Le Vet B.V.
VMD MA No.
19994/4018
What it's used for
Sedation. Premedication in combination with an anaesthetic.
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Clinical information
Nerfasin 100 mg/ml, Solution for Injection for Cattle and Horses — SPC Details
Source: VMD Summary of Product Characteristics (SPC). Last updated 26 Mar 2026.
Sedation.
Premedication in combination with an anaesthetic.
Premedication in combination with an anaesthetic.
Cattle: intramuscular.
Horses: intravenous.
To ensure a correct dosage body weight should be determined as accurately
as possible.
The intravenous injection to horses should be given slowly.
Cattle:
Dosage:
Dosage for cattleDosage level*xylazine
(mg/kg)
Nerfasin vet. 100
mg/ml
(ml/100 kg)
Nerfasin vet. 100
mg/ml
(ml/500 kg)
I0.050.050.25II0.10.10.5III0.20.21IV0.30.31.5
*Dose 1: Sedation, with a slight decrease of muscle tone. The ability to stand is
maintained.
Dose 2: Sedation, marked decrease of muscle tone and some analgesia. The
animal usually remains standing, but may lie down.
Dose 3: Deep sedation, further decrease of muscle tone and a degree of
analgesia. The animal lies down.
Dose 4: Very deep sedation, a profound decrease in muscle tone and a degree
of analgesia. The animal lies down.
Horses
Dosage:
(0.6-1 ml product per 100 kg body weight).
The stopper should not be punctured more than 20 times.
Revised: August 2017
AN: 01202/2016
The number of punctures should be recorded on the outer packaging
Horses: intravenous.
To ensure a correct dosage body weight should be determined as accurately
as possible.
The intravenous injection to horses should be given slowly.
Cattle:
Dosage:
Dosage for cattleDosage level*xylazine
(mg/kg)
Nerfasin vet. 100
mg/ml
(ml/100 kg)
Nerfasin vet. 100
mg/ml
(ml/500 kg)
I0.050.050.25II0.10.10.5III0.20.21IV0.30.31.5
*Dose 1: Sedation, with a slight decrease of muscle tone. The ability to stand is
maintained.
Dose 2: Sedation, marked decrease of muscle tone and some analgesia. The
animal usually remains standing, but may lie down.
Dose 3: Deep sedation, further decrease of muscle tone and a degree of
analgesia. The animal lies down.
Dose 4: Very deep sedation, a profound decrease in muscle tone and a degree
of analgesia. The animal lies down.
Horses
Dosage:
(0.6-1 ml product per 100 kg body weight).
The stopper should not be punctured more than 20 times.
Revised: August 2017
AN: 01202/2016
The number of punctures should be recorded on the outer packaging
• Do not use in case of hypersensitivity to the active substance or to any of the
excipients.
•
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 cattle weighing less than 200 kg bodyweight. 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 section 4.7).
Revised: August 2017
AN: 01202/2016
excipients.
•
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 cattle weighing less than 200 kg bodyweight. 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 section 4.7).
Revised: August 2017
AN: 01202/2016
Revised: August 2017
AN: 01202/2016
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.
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.
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).
AN: 01202/2016
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.
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.
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).
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.
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 results 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
Revised: August 2017
AN: 01202/2016
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.
• 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.
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 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.
• 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.
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 results 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
Revised: August 2017
AN: 01202/2016
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.
• 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.
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 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.
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/Sulphonamide containing
products should not be undertaken when horses have been sedated with
xylazine.
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/Sulphonamide containing
products should not be undertaken when horses have been sedated with
xylazine.
Do not refrigerate or freeze.
Cattle:
Meat and offal: 1 day
Milk: zero hours
Horses:
Meat and offal: 1 day
Milk: zero hours
5.
Meat and offal: 1 day
Milk: zero hours
Horses:
Meat and offal: 1 day
Milk: zero hours
5.
This information is sourced from the official Summary of Product Characteristics (SPC) published by the Veterinary Medicines Directorate (VMD). It is provided for informational purposes only and does not replace professional veterinary advice. Always consult your vet before administering any medication.
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Same active ingredient
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