POM-V Prescription Required Companion Animal

Isoflurin 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

Vetpharma Animal Health, S.L

VMD MA No.

32509/3006

What it's used for

Induction and maintenance of general anaesthesia.

Full indications, dosage and side effects ↓

View official SPC (PDF)

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Paying less for Isoflurane

1

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2

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Clinical information

Isoflurin 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 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. The use of analgesia for
painful procedures is consistent with good veterinary practice.
Recovery from isoflurane anaesthesia is usually smooth and rapid. The analgesic
requirements of the patient should be considered before the termination of general
anaesthesia.
Although anaesthetics have a low potential for damage to the atmosphere, it is good
practice to use charcoal filters with scavenging equipment, rather than to discharge
them into the air.
HORSES
The MAC for isoflurane in the horse is approximately 13.1 mg/g.
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, alfentanil, atracurium, butorphanol, detomidine, diazepam,
dobutamine, dopamine, guiaphenesin, ketamine, morphine, pentazocine, 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
Detomidine and xylazine have been reported to reduce the MAC for isoflurane in
horses.
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 guiaphenesin. Concentrations of 30 to 50 mg/g isoflurane may
then be used to achieve the desired depth of anaesthesia in 5 to 10 minutes.
Isoflurane at a concentration of 30 to 50 mg/g in a high flow oxygen may be used for
induction in foals.
Maintenance
Anaesthesia may be maintained using 15 to 25 mg/g isoflurane.
Recovery
Recovery is usually smooth and rapid.
AN: 03293/2024 & 03296/2024
DOGS
The MAC for isoflurane in the dog is approximately 12.8 mg/g.
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, etomidate, 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
Morphine, oxymorphone, acepromazine, medetomidine, medetomidine plus
midazolam have been reported to reduce the MAC for isoflurane in dogs.
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 β-receptor activity.
Induction
Induction is possible by face mask using up to 50 mg/g isoflurane, with or without
premedication.
Maintenance
Anaesthesia may be maintained using 15 to 25 mg/g isoflurane.
Recovery
Recovery is usually smooth and rapid.
CATS
The MAC for isoflurane in the cat is approximately 16.3 mg/g.
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, atracurium, 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
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).
Induction
Induction is possible by face mask using up to 40 mg/g isoflurane, with or without
premedication.
AN: 03293/2024 & 03296/2024
Maintenance
Anaesthesia may be maintained using 15 to 30 mg/g isoflurane.
Recovery
Recovery is usually smooth and rapid.
ORNAMENTAL BIRDS
Few MAC/ED50 values have been recorded. Examples are 13.4 mg/g for the Sandhill
crane, 14.5 mg/g for the racing pigeon, reduced to 8.9 mg/g by the administration of
midazolam, and 14.4 mg/g for cockatoos, reduced to 10.8 mg/g 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
Butorphanol has been reported to reduce the MAC for isoflurane in cockatoos.
Midazolam has been reported to reduce the MAC for isoflurane in pigeons.
Induction
Induction with 30 to 50 mg/g 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, 20 to 30
mg/g is suitable and safe.
Only 6 to 10 mg/g may be needed for some stork and heron species.
Up to 40 to 50 mg/g may be needed for some vultures and eagles.
35 to 40 mg/g 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
Isoflurane is considered by several authors to be the anaesthetic of choice for many
species. The literature records its 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 31.4 mg/g at 35ºC and 28.3 mg/g
at 20ºC.
Drug interactions/ compatibilities
No specific publications on reptiles have reviewed compatibilities or interactions of
other drugs with isoflurane anaesthesia.
Induction
Induction is usually rapid at 20 to 40 mg/g isoflurane.
Maintenance
10 to 30 mg/g is a useful concentration
AN: 03293/2024 & 03296/2024
Recovery
Recovery is usually smooth and rapid
RATS, MICE, HAMSTERS, CHINCHILLAS, GERBILS, GUNIEA PIGS AND
FERRETS
Isoflurane has been recommended for anaesthesia of a wide variety of small
mammals.
The MAC for mice has been cited as 13.4 mg/g, and for the rat as 13.8 mg/g, 14.6
mg/g and 24 mg/g.
Drug interactions/ compatibilities
No specific publications on small mammals have reviewed compatibilities or
interactions of other drugs with isoflurane anaesthesia.
Induction
Isoflurane concentration 20 to 30 mg/g.
Maintenance
Isoflurane concentration 2.5 to 20 mg/g.
Recovery
Recovery is usually smooth and rapid.
Guide to induction and maintenance of anaesthesia by species
SpeciesMAC (%)Induction
(%)
Maintenance
(%)
RecoveryHorses1.313.0 – 5.0
(foals)
1.5 – 2.5Smooth and
rapid
Dogs1.28Up to 5.01.5 – 2.5Smooth and
rapid
Cats1.63Up to 4.01.5 – 3.0Smooth and
rapid
Ornamental birdsSee 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 – 2.0Smooth and
rapid

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

Horse, dog, cat, ornamental bird, reptile, rat, mouse, hamster, chinchilla, gerbil, guinea
pig, ferret:
Rare
(1 to 10 animals / 10,000 animals
treated):
Arrhythmia, bradycardia
Very rare
(<1 animal / 10,000 animals treated,
including isolated reports):
Cardiac arrest
Respiratory arrest
Malignant hyperthermia
Undetermined frequency
(cannot be estimated from the available
data):
Hypotension
Respiratory depression
1
Transient
Susceptible animals
Dose-related
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 ease and rapidity of alteration of the depth of anaesthesia with isoflurane and its
low metabolism, may be considered advantageous for its use in special groups of
patients such as the old or young, and those with impaired hepatic, renal or cardiac
function.

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 the general anaesthesia is ended.
The use of the product in patients with cardiac disease should be considered only after
a risk/ benefit assessment by the veterinarian.
AN: 03293/2024 & 03296/2024
It is important to monitor breathing and pulse for the frequency and its features.
Respiratory arrest should be treated by assisted ventilation. It is important to maintain
airways free and properly oxygenate tissues during the maintenance of anaesthesia.
In the case of cardiac arrest, perform a complete cardiopulmonary resuscitation.
The metabolism of isoflurane in birds and small mammals, can be affected by
decreases in body temperature, that may occur secondary to a high surface area to
body weight ratio. Therefore, body temperature should be monitored and kept stable
during treatment.
Drug metabolism in reptiles is slow and highly dependent upon environmental
temperature. Reptiles may be difficult to induce with inhalation agents due to breath
holding.
Like other inhalation anaesthetics of this type, isoflurane depresses the respiratory
and cardiovascular systems.
When using isoflurane to anaesthetise an animal with a head injury, consideration
should be given as to whether artificial ventilation is appropriate to help avoid
increased cerebral blood flow by maintaining normal CO2 levels.
Special precautions to be taken by the person administering the veterinary medicinal
product to animals
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.
Exposure to anaesthetics can harm the unborn child. The veterinary medicinal
product should not be administered by pregnant women. Pregnant and breast-
feeding women 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 the product
during maintenance of general anaesthesia.
Care should be taken when dispensing isoflurane, with any spillage removed
immediately using an inert and absorbent material e.g. sawdust. 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 label.
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.
AN: 03293/2024 & 03296/2024

The action of muscle relaxants in man, especially those of the nondepolarising
(competitive) type such as atracurium, pancuronium or vecuronium, is enhanced by
isoflurane. Similar potentiation might be expected to occur in the target species,
although there is little direct evidence to this effect. 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 produce and maintain anaesthesia. Some examples are given
in section

Do not store above 25ºC.
Store in the original container.
Protect from light.
Keep the bottle tightly closed.

(foals)
1.5 – 2.5Smooth and
rapid
Dogs1.28Up to 5.01.5 – 2.5Smooth and
rapid
Cats1.63Up to 4.01.5 – 3.0Smooth and
rapid
Ornamental birdsSee 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 – 2.0Smooth 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
AN: 03293/2024 & 03296/2024
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.
Not applicable.
3.12 Withdrawal period
Horses: Meat and offal: 2 days
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.