POM-V Prescription Required Companion Animal

Vetflurane 1000 mg/g Inhalation Vapour, Liquid

Active ingredient: Isoflurane

Form

Inhalation vapour, liquid

Species

Cats Chinchilla Dogs Ferrets Gerbil Guinea Pig Hamster Horses Mouse Ornamental Birds Rat Reptiles

Manufacturer

Virbac

VMD MA No.

05653/3027

What it's used for

Induction and maintenance of general anaesthesia.

Full indications, dosage and side effects ↓

View official SPC (PDF)

The prescription itself has a price. See what practices near you charge for a consultation and the written prescription fee.

Paying less for Isoflurane

1

Ask your vet for a written prescription

They must provide one on request. Under the CMA Order the fee is capped at £21 from 2027.
2

Fill it at a registered online retailer

The CMA found online pharmacies 50–60% cheaper than practice dispensing on common medicines — typically £200–£300 a year.

Your prescription rights → VMD register of retailers →

Prescription required

Your vet must provide a written prescription on request. You can then purchase from any licensed online retailer.

Clinical information

Vetflurane 1000 mg/g Inhalation Vapour, Liquid — SPC Details

Source: VMD Summary of Product Characteristics (SPC). Last updated 27 Mar 2026.

Induction and maintenance of general anaesthesia.

Isoflurane should be administered using an accurately calibrated vaporiser in an
appropriate anaesthetic circuit, since levels of anaesthesia may be altered rapidly and
easily.
Isoflurane may be administered in oxygen or oxygen/nitrous oxide mixtures.
The MAC (minimal alveolar concentration in oxygen) or effective dose ED50 values and
suggested concentrations given below for the target species should be used as a guide or
starting point only. The actual concentrations required in practice will depend on many
variables, including the concomitant use of other drugs during the anaesthetic procedure
and the clinical status of the patient.
Isoflurane may be used in conjunction with other drugs commonly used in veterinary
anaesthetic regimes for premedication, induction and analgesia. Some specific examples
are given in the individual species information.
Recovery from isoflurane anaesthesia is usually smooth and rapid. The analgesic
requirements of the patient should be considered before the termination of general
anaesthesia.
The concurrent use of sedative or analgesic drugs is likely to reduce the level of isoflurane
required to produce and maintain anaesthesia.
HORSE
The MAC for isoflurane in the horse is approximately 1.31%
Premedication
Isoflurane may be used with other drugs commonly used in veterinary anaesthetic
regimes. The following drugs have been found to be compatible with isoflurane:
acepromazine, butorphanol, detomidine, diazepam, dobutamine, dopamine, guaiphenesin,
ketamine, morphine, pethidine, thiamylal, thiopentone and xylazine. Drugs used for
premedication should be selected for the individual patient. However, the potential
interactions below should be noted.
Interactions
See section 3.8.
Induction
As it is not normally practicable to induce anaesthesia in adult horses using isoflurane,
induction should be by the use of a short acting barbiturate such as thiopentone sodium,
ketamine or guaiphenesin. Concentrations of 3 to 5% isoflurane may then be used to
achieve the desired depth of anaesthesia in 5 to 10 minutes
Isoflurane at a concentration of 3 to 5% in a high flow oxygen may be used for induction in
foals.
Maintenance
Anaesthesia may be maintained using 1.5% to 2.5% isoflurane.
Recovery
Recovery is usually smooth and rapid.
DOG
The MAC for isoflurane in the dog is approximately 1.28%.
Premedication
Isoflurane may be used with other drugs commonly used in veterinary anaesthetic
regimes. The following drugs have been found to be compatible with isoflurane:
acepromazine, atropine, butorphanol, buprenorphine, bupivacaine, diazepam, dobutamine,
ephedrine, epinephrine, glycopyrrolate, ketamine, medetomidine, midazolam,
methoxamine, oxymorphone, propofol, thiamylal, thiopentone and xylazine. Drugs used for
premedication should be selected for the individual patient. However, the potential
interactions below should be noted.
Interactions
See section 3.8.
Induction
Induction is possible by face mask using up to 5% isoflurane, with or without
premedication.
Maintenance
Anaesthesia may be maintained using 1.5% to 2.5% isoflurane.
Recovery
Recovery is usually smooth and rapid.
CAT
The MAC for isoflurane in the cat is approximately 1.63%.
Premedication
Isoflurane may be used with other drugs commonly used in veterinary anaesthetic
regimes. The following drugs have been found to be compatible with isoflurane:
acepromazine, atropine, diazepam, ketamine, and oxymorphone. Drugs used for
premedication should be selected for the individual patient. However, the potential
interactions below should be noted.
Interactions
See section 3.8.
Induction
Induction is possible by face mask using up to 4% isoflurane, with or without
premedication.
Maintenance
Anaesthesia may be maintained using 1.5% to 3% isoflurane.
Recovery
Recovery is usually smooth and rapid.
ORNAMENTAL BIRDS
Few MAC/ED50 values have been recorded. Examples are 1.34% for the Sandhill crane,
1.45% for the racing pigeon, reduced to 0.89% by the administration of midazolam, and
1.44% for cockatoos, reduced to 1.08% by the administration of butorphanol analgesic.
The use of isoflurane anaesthesia has been reported for many species, from small birds
such as zebra finches, to large birds such as vultures, eagles and swans.
Drug interactions/compatibilities
Propofol has been demonstrated in the literature to be compatible with isoflurane
anaesthesia in swans.
Interactions
See section 3.8.
Induction
Induction with 3 to 5% isoflurane is normally rapid. Induction of anaesthesia with propofol,
followed by isoflurane maintenance, has been reported for swans.
Maintenance
The maintenance dose depends on the species and individual. Generally, 2 to 3% is
suitable and safe.
Only 0.6 to 1% may be needed for some stork and heron species.
Up to 4 to 5% may be needed for some vultures and eagles.
3.5 to 4% may be needed for some ducks and geese.
Generally, birds respond very rapidly to changes in concentration of isoflurane.
Recovery
Recovery is usually smooth and rapid.
REPTILES
The literature records isoflurane’s use on a wide variety of reptiles (eg. various species of
lizard, tortoise, iguanas, chameleon and snakes).
The ED50 was determined in the desert iguana to be 3.14% at 35˚C and 2.83% at 20˚C.
Drug interactions/ compatibilities
See section 3.8.
Induction
Induction is usually rapid at 2 to 4% isoflurane.
Maintenance
1 to 3% is a useful concentration
Recovery
Recovery is usually smooth and rapid
RATS, MICE, HAMSTERS, CHINCHILLAS, GERBILS, GUINEA PIGS AND FERRETS
The MAC for mice has been cited as 1.34%, and for the rat as 1.38%, 1.46% and 2.4%.
Drug interactions/ compatibilities
See section 3.8.
Inducti on
Isoflurane concentration 2 to 3%.
Maintenance
Isoflurane concentration 0.25 to 2%.
Recovery
Recovery is usually smooth and rapid.
SpeciesMAC (%)Induction (%)Maintenance
(%)
RecoveryHorse1.313.0 – 5.0
(foals)
1.5 – 2.5Smooth and
rapid
Dog1.28Up to 5.01.5 – 2.5Smooth and
rapid
Cat1.63Up to 4.01.5 – 3.0Smooth and
rapid
Ornamental
birds
See posology3.0 – 5.0See posologySmooth and
rapid
ReptilesSee posology2.0 – 4.01.0 – 3.0Smooth and
rapid
Rats, mice,
hamsters,
chinchillas,
gerbils, guinea
pigs and ferrets
1.34 (mouse)
1.38/1.46/2.40
(rat)
2.0 – 3.00.25 – 2.0
Smooth and
rapid

Do not use in case of known susceptibility to malignant hyperthermia.
Do not use in cases of known hypersensitivity to isoflurane or to other halogenated agents.

Horses, dogs, cats, ornamental birds, reptiles, rats, mice, hamsters, chinchillas, gerbils,
guinea pigs and ferrets.
Rare
(1 to 10 animals / 10,000
animals treated):
Arrythmia, Bradycardia
Very rare
(<1 animal / 10,000 animals
treated, including isolated
reports):
Malignant hyperthermia
2Undetermined frequency
(cannot be estimated from the
available data)
Hypotension
, Cardiac arrest
Respiratory depression
, Respiratory arrest
1
Transient.
In susceptible animals.
In a dose-related manner.
In the case of cardiac arrest, perform a complete cardio pulmonary resuscitation.
Respiratory arrest should be treated by assisted ventilation.
Reporting adverse events is important. It allows continuous safety monitoring of a
veterinary medicinal product. Reports should be sent, preferably via a veterinarian, to
either the marketing authorisation holder or its local representative or the national
competent authority via the national reporting system. See the package leaflet for
respective contact details.

The metabolism of birds, and to an extent small mammals, is affected more profoundly by
decreases in body temperature, due to high surface area to body weight ratio. Drug
metabolism in reptiles is slow and highly dependent upon environmental temperature.
The absorption, distribution and elimination of isoflurane are rapid, and it is eliminated
largely unchanged via the lungs. These characteristics may make it suitable for groups of
patients including the young or old, or those with impaired hepatic, renal or cardiac
function, however anaesthetic protocols should be decided on a case by case basis.

Special precautions for safe use in the target species:
Isoflurane has little or no analgesic properties. Adequate analgesia should always be given
before surgery. The analgesic requirements of the patient should be considered before
general anaesthesia is ended.
The use of the veterinary medicinal product in patients with cardiac disease should be
considered only after a benefit-risk assessment by the responsible veterinarian.
It’s important to monitor breathing and pulse for the frequency and its features. It’s
important to maintain airways free and properly oxygenate tissues during the maintenance
of anaesthesia.
When using isoflurane to anaesthetise an animal with a head injury, consideration should
be given as to whether artificial ventilation is appropriate to maintain normal CO2 levels, so
that cerebral blood flow does not increase.
As isoflurane is a respiratory depressant, it could be advised to monitor the respiratory rate
and depth during anaesthesia.
Special precautions to be taken by the person administering the veterinary medicinal
product to animals:
In case of a known hypersensitivity to isoflurane, the professional must not handle this
veterinary medicinal product.
Do not breathe the vapour.
Users should consult their National Authority for advice on Occupational Exposure
Standards for isoflurane.
Operating rooms and recovery areas should be provided with adequate ventilation or
scavenging systems to prevent the accumulation of anaesthetic vapour. All
scavenging/extraction systems must be adequately maintained.
Pregnant and breastfeeding women should not have any contact with the veterinary
medicinal product and should avoid operating rooms and animal recovery areas.
Avoid using masking procedures for prolonged induction and maintenance of general
anaesthesia.
Use cuffed endotracheal intubation when possible for the administration of this veterinary
medicinal product during maintenance of general anaesthesia.
Wash any splashes from skin and eyes, and avoid contact with the mouth. If severe
accidental exposure occurs remove the operator from the source of exposure, seek urgent
medical assistance and show the package leaflet or the label to the physician.
Halogenated anaesthetic agents may induce liver damage. In case of isoflurane this is an
idiosyncratic response very rarely seen after repeated exposure.
Advice to Doctors:
treatment. Note that adrenaline and catecholamines may cause cardiac dysrhythmias.
Special precautions for the protection of the environment:
To protect the environment, it is considered good practice to use charcoal filters with
scavenging equipment.
Care should be taken when dispensing isoflurane, with any spillage removed immediately
using an inert and absorbent material e.g. sawdust.

Concurrent inhalation of nitrous oxide enhances the effect of isoflurane in man and similar
potentiation might be expected in animals.
The concurrent use of sedative or analgesic drugs is likely to reduce the level of isoflurane
required to induce and maintain anaesthesia.
In horses, detomidine and xylazine have been reported to reduce MAC for isoflurane.
In dogs, morphine, oxymorphone, acepromazine, medetomidine plus midazolam have
been reported to reduce the MAC for isoflurane. The concomitant administration of
midazolam/ketamine during isoflurane anaesthesia may result in marked cardiovascular
effects, particularly arterial hypotension. The depressant effects of propanolol on
myocardial contractility are reduced during isoflurane anaesthesia, indicating a moderate
degree of -receptor activity.
In cats, intravenous administration of midazolam-butorphanol has been reported to alter
several cardio-respiratory parameters in isoflurane-induced cats as has epidural fentanyl
and medetomidine. Isoflurane has been shown to reduce the sensitivity of the heart to
adrenaline (epinephrine).
In cockatoos, butorphanol has been reported to reduce the MAC for isoflurane.
In pigeons, midazolam has been reported to reduce the MAC for isoflurane.
For reptiles and small mammals, there are no data available.
Isoflurane has a weaker sensitising action on the myocardium, to the effects of circulating
dysrhythmogenic catecholamines, than halothane.
Isoflurane may be degraded to carbon monoxide by dried carbon dioxide absorbents.

Do not store above 25 C.
Protect from direct sunlight.
Store in the original container.
Keep the bottle tightly closed.

(foals)
1.5 – 2.5Smooth and
rapid
Dog1.28Up to 5.01.5 – 2.5Smooth and
rapid
Cat1.63Up to 4.01.5 – 3.0Smooth and
rapid
Ornamental
birds
See posology3.0 – 5.0See posologySmooth and
rapid
ReptilesSee posology2.0 – 4.01.0 – 3.0Smooth and
rapid
Rats, mice,
hamsters,
chinchillas,
gerbils, guinea
pigs and ferrets
1.34 (mouse)
1.38/1.46/2.40
(rat)
2.0 – 3.00.25 – 2.0
Smooth and
rapid
3.10 Symptoms of overdose (and where applicable, emergency procedures and
antidotes)
Isoflurane overdose may result in profound respiratory depression. Therefore, respiration
must be monitored closely and supported when necessary with supplementary oxygen
and/ or assisted ventilation.
In cases of severe cardiopulmonary depression, administration of isoflurane should be
discontinued, the breathing circuit should be flushed with oxygen, the existence of a patent
airway ensured, and assisted or controlled ventilation with pure oxygen initiated.
Cardiovascular depression should be treated with plasma expanders, pressor agents,
antiarrhythmic agents or other appropriate techniques.
3.11 Special restrictions for use and special conditions for use, including
restrictions on the use of antimicrobial and antiparasitic veterinary
medicinal products in order to limit the risk of development of resistance
3.12 Withdrawal periods
Horses
Meat and offal: 2 days.
Milk: Not authorised for use in mares producing milk for human consumption.
4.

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.