POM-V Prescription Required Companion Animal

Iso-Vet 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 Pigs Rat Reptiles

Manufacturer

Piramal Critical Care B.V.

VMD MA No.

51310/3000

What it's used for

Horses, dogs, cats, ornamental birds, reptiles, rats, mice, hamsters, chinchillas, gerbils, guinea pigs and ferrets: Induction and maintenance of general a...

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

Iso-Vet 1000 mg/g Inhalation Vapour, Liquid — SPC Details

Source: VMD Summary of Product Characteristics (SPC). Last updated 26 Mar 2026.

Horses, dogs, cats, ornamental birds, reptiles, rats, mice, hamsters,
chinchillas, gerbils, guinea pigs and ferrets: Induction and maintenance of
general anaesthesia
Piglets (up to 7 days of age):
For general anaesthesia during the castration of male piglets in
combination with the preoperative parenteral administration of a suitable
analgesic to relieve postoperative pain.

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.
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.

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, alfentanil, atracurium,
butorphanol, detomidine, diazepam, dobutamine, dopamine,
guaiphenesin, 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.

Revised: December 2025
AN: 02867/2025
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 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, 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.

Revised: December 2025
AN: 02867/2025
The concomitant administration of midazolam/ketamine during isoflurane
anaesthesia may result in marked cardiovascular effects, particularly
arterial hypotension.
The depressant effects of propranolol on myocardial contractility are
reduced during isoflurane anaesthesia, indicating a moderate degree of
receptor activity.
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, 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 4% isoflurane, with or
without premedication.

Revised: December 2025
AN: 02867/2025
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
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 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.

Revised: December 2025
AN: 02867/2025
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 3.14% at
2.83% at 20˚C.
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 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
Isoflurane has been recommended for anaesthesia of a wide variety of
small mammals.
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
No specific publications on small mammals have reviewed compatibilities
or interactions of other drugs with isoflurane anaesthesia.

Revised: December 2025
AN: 02867/2025
Induction
Isoflurane concentration 2 to 3%.
Maintenance
Isoflurane concentration 0.25 to 2%.
Recovery
Recovery is usually smooth and rapid.
PIGS (CASTRATION OF PIGLETS UP TO 7 DAYS OF AGE):
For piglets (up to 7 days of age)
Isoflurane concentration of up to 5Vol%, with oxygen as carrier gas with a
flow rate of 2L/min.
The MAC value for isoflurane in pigs is 1.41-2.00%.
Premedication:
Post-operative pain must be controlled by the timely parenteral
administration of appropriate analgesics before the induction of
anaesthesia.
Induction:
Isoflurane concentrations of up to 5 Vol % are used for the anaesthetic
induction (with oxygen as carrier gas with a flow rate of 2L/min). After 70-
90 seconds a sufficient depth of anaesthesia is generally achieved. The
actual duration required in practice depends on many variables. It is
therefore imperative that the depth of anaesthesia be clinically checked by
means of reflexes in each individual animal before castration is started.
The inter- and dew claw reflexes are particularly suitable.
The castration may only be carried out under controlled supply of
isoflurane, using a suitable inhalation device tested for the purpose. For
the individual animal, it must be ensured that the mask used is leak-proof
and that the exhaust air is filtered and discharged into a room
(e.g. outdoors) where a sufficient rate of air exchange is achieved.
The product should only be used for uncomplicated castration procedures
that are anticipated to be short in duration (maximum of 120 seconds for
the entire procedure from the induction of anaesthesia to the end of
castration of a piglet).

Revised: December 2025
AN: 02867/2025
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
posology
Smooth 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
Pigs (piglets
up to 7 days
of age)
1.41-2.00Up to 5.0-Smooth and
rapid

Do not use in cases of known susceptibility to malignant hyperthermia.
Do not use in cases of known hypersensitivity to isoflurane.

Isoflurane produces hypotension and respiratory depression in a dose-
related manner. Cardiac arrhythmias and transient bradycardia have been
reported rarely.

Revised: December 2025
AN: 02867/2025
Malignant hyperthermia has been reported very rarely in susceptible
animals.
Isoflurane may produce excitations (tremors, restlessness), pale mucous
membranes and prolonged recovery time
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 treated)
- uncommon (more than 1 but less than 10 animals in 1,000 animals
treated)
- rare (more than 1 but less than 10 animals in 10,000 animals treated)
- very rare (less than 1 animal in 10,000 animals treated, including isolated
reports).

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.

Revised: December 2025
AN: 02867/2025
Piglets (up to 7 days of age):
When using a system which does not allow individual adjustment of the
delivered dosage to each piglet, attention should be paid to the
homogeneity of the group of animals to be anaesthetized simultaneously,
in terms of age and weight. Care must be taken to ensure that the
anaesthetic mask fits securely and tightly in order to guarantee a sufficient
depth of anaesthesia for each individual animal.
To ensure safe and reliable anaesthesia, the sufficient depth of
anaesthesia should be verified by appropriate reflex testing in each
individual animal before the start of a painful procedure.
The use of a multimodal perioperative pain management is recommended.

Special precautions for use in animals
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 product in patients with cardiac disease should be
considered only after a risk/ benefit assessment by the veterinarian.
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.

Revised: December 2025
AN: 02867/2025
Piglets (up to 7 days of age):
Piglets should be observed for a sufficiently long time after castration in
order to be able to recognise and, if necessary, treat post-operative
bleeding.
Care must be taken to ensure that the piglets do not cool down and, when
awake, are returned to the mother sow as soon as possible.
Do not use in piglets with anatomical anomalies in the genital area
(e.g. cryptorchidism).
Special precautions to be taken by the person administering the veterinary
medicinal product to animals
Isoflurane induces anaesthesia in humans. Moreover, it may induce liver
damage and also allergic reactions to isoflurane have been reported.
Fatigue, headache, or reduced reaction times have been reported at
exposures below therapeutic doses. Splashes to the eye may induce
irritation.
Do not breathe the vapour. Wash any splashes from skin and eyes, and
avoid contact with the mouth.
Care should be taken when dispensing isoflurane, with any spillage
removed immediately using an inert and absorbent material e.g. sawdust.
Contaminated work clothing should be taken off and washed before reuse.
Operating rooms and recovery areas should be provided with adequate
ventilation or scavenging systems to prevent the accumulation of
anaesthetic vapour. Avoid using masking procedures for prolonged
induction and maintenance of general anaesthesia. Use cuffed
endotracheal intubation when possible for the administration of isoflurane
during maintenance of general anaesthesia.
In the event of isoflurane odour or adverse health effects such as
dizziness etc remove from the source of exposure and go to fresh air. In
case of severe accidental exposure seek urgent medical assistance and
show this label.
Isoflurane passes the placenta and transfers from maternal to foetal blood.
Adverse effects on foetuses and pregnant animals were observed in
laboratory animals. Pregnant and/or breast- feeding women should not
have any contact with the product and should avoid operating rooms and
animal recovery areas.

Revised: December 2025
AN: 02867/2025
Adverse effects on male fertility cannot be excluded. In male rats, effects
on fertility parameters were observed after repeated exposure at higher
concentrations. Prevent inhalation exposure to high concentrations by
carefully following the instructions in the product information.
Piglets (up to 7 days of age)
In order to ensure that the safety of the workplace is maintained,
castration may only be carried out using an appropriate inhalation device
equipped with scavenging double masks.
The exposure of the user should be kept as low as possible. Operating
theatres and recovery areas should be equipped with adequate ventilation
to prevent accumulation of isoflurane vapours in the air breathed. In the
case of underfloor ventilation, artificial ventilation must be set.
When the anaesthetic gas is used in a pig holding, a suitable isoflurane
filling device should be used. Isoflurane tanks should preferably be filled
outdoors, but at least in very well- ventilated rooms outside the rooms
where animals are kept, with as few staff in the room as possible. It is
recommended that the filling of isoflurane is monitored by additional
personnel not involved in the filling process in case of an accidental
exposure event.
Vaporizers should be switched off when not in use. It is advisable to have
an isoflurane container with a capacity adapted to the amount needed for
a whole day, so that the container does not need to be filled during
anaesthesia.
It must be ensured that the mask used seals tightly for each individual
piglet in order to avoid additional exposure of the workplace.
from an unoccupied anaesthesia mask (no piglets in anaesthesia mask)
must be prevented.
To the physician: Ensure a patient airway is clear and give symptomatic
and supportive treatment. Note that adrenaline and catecholamines may
cause cardiac arrhythmias.’
4.5 iii) Other Precautions
potential and ozone depletion potential; thus it is good practice to use
charcoal filters with scavenging equipment, rather than to discharge the
gas into the air.

interaction
The action of muscle relaxants in man, especially those of the
nondepolarizing (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. For
example, opiates, alpha-2-agonists, acepromazine, and benzodiazepines
have been reported to reduce the MAC values.
The same was reported with the simultaneous use of non-steroidal anti-
inflammatory drugs in the castration of piglets.
Some examples are given in 4.9.

Revised: December 2025
AN: 02867/2025
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 & direct heat.
Store in tightly closed original container.

Revised: December 2025
AN: 02867/2025

(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
posology
Smooth 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
Pigs (piglets
up to 7 days
of age)
1.41-2.00Up to 5.0-Smooth and
rapid
4.10 Overdose (symptoms, emergency procedures, antidotes) if
necessary
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.
4.11 Withdrawal period(s)
Horses:
Meat and offal: 2 days
Not authorised for use in mares producing milk for human consumption.
Pigs (piglets up to 7 days of age):
Meat and offal: 2 days

Revised: December 2025
AN: 02867/2025
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.