POM-V Prescription Required Companion Animal

Isofane 100% w/w Inhalation Vapour, Liquid

Active ingredient: Isoflurane

Form

Solution

Species

Cats Dogs Horses Mouse Ornamental Birds Rabbits Rat Reptiles

Manufacturer

Piramal Critical Care Limited

VMD MA No.

37071/5002

What it's used for

To induce and maintain anaesthesia in all types of veterinary surgery.

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

Isofane 100% w/w Inhalation Vapour, Liquid — SPC Details

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

To induce and maintain anaesthesia in all types of veterinary surgery.

Do not use in animals sensitive to isoflurane or other halogenated or inhalation
anaesthetic agents. Do not use in animals with a known susceptibility to malignant
hyperthermia.

Heart rate usually remains stable with isoflurane, however both respiration and
blood pressure are depressed in a dose-related manner. Pulse and respiration
should be assessed for both rate and character in all patients. Consideration
should be given to supplemental ventilation, especially in animals which have
sustained injuries which may lead to increased CO2 levels or a depressed heart
rate. In animals with head injuries consider supplemental ventilation to maintain
normal circulating CO2 levels such that cerebral blood flow does not increase.
Blood pressure should be assessed throughout anaesthesia. Hypotension, if
related to depth of anaesthesia, can be corrected by a reduction in delivered
isoflurane concentration.
In horses, as with all anaesthetic agents, it may sometimes be necessary to
administer an ionotropic agent in hypotension. Isoflurane appears to sensitise the
myocardium to the dysrhythmogenic effects of circulating catecholamines to a
lesser extent than halothane.

Revised: November 2025
MA split from NI Expiry following AN: 02521/2025Page 3 of 6

Horses: Recovery from isoflurane anaesthesia is generally smooth and rapid.
However, one report suggests that horses recovering from isoflurane anaesthesia
may appear un-coordinated. It is important to provide adequate post-anaesthetic
analgesia since isoflurane anaesthetised horses may become aware of their
surroundings more rapidly than horses recovering from halothane anaesthesia.
Other species: none

Revised: November 2025
MA split from NI Expiry following AN: 02521/2025Page 2 of 6

i.
Special precautions for use in animals None known
ii.
Special precautions for the person administering the veterinary medicinal
product to animals
Do not breathe the vapour. The Occupational Exposure Standard (OES) for
isoflurane has been set at 50 ppm on an 8-hour weighted average.
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. To protect the
environment it is considered good practice to use charcoal filters with
scavenging/ventilation equipment.
Avoid using masking procedures for prolonged induction and maintenance of
general anaesthesia. Use cuffed endotracheal intubation when possible for the
administration of Isofane 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.
Pregnant and breast-feeding women should avoid exposure to the product and
should avoid operating rooms and animal recovery areas.
Wash any splashes from skin and eyes immediately and avoid contact with the
mouth.
In the event of severe accidental exposure; remove the operator from the
source of the exposure and seek urgent medical assistance and show this label.
Halogenated anaesthetic agents may induce liver damage. In the case of
isoflurane this is an idiosyncratic response very rarely seen after repeated
exposure.
Advice to doctors: maintain a patent airway and give symptomatic and
supportive treatment. Note that adrenaline and catecholamines may cause cardiac
dysrhythmias.

interaction
Muscle relaxation with isoflurane is normally adequate for the majority of surgical
procedures. If a more profound muscle relaxation is required, e.g. for thoracic
surgery, additional muscle relaxants may be employed. All commonly available
non-depolarising muscle relaxants are potentiated by isoflurane and the effects will
be maintained for longer than is usual with these agents. In dogs, care should be
taken if administering a midazolamketamine combination to an animal already
anaesthetised with isoflurane.

Do not store above 25°C.
Keep the container tightly closed. Protect from light.

Revised: November 2025
MA split from NI Expiry following AN: 02521/2025Page 6 of 6

(Foals)
1.5 – 2.51.31DogUp to 5.01.5 – 2.51.3CatUp to 4.01.5 – 3.01.61Ornamental birdsUp to 5.02.0 – 3.01.5Reptiles2.0 - 4.01.0 – 3.0N/aSmall Mammals2.0 – 3.00.25 – 2.0Rabbit 2.05
Mouse 1.34
Rat 1.38 – 2.4
* Minimum Alveolar Concentration at which 50% of anaesthetised patients show
no response to a stimulus.
4.10
Overdose (symptoms, emergency procedures, antidotes), if
necessary
Isoflurane causes dose related respiratory and cardiovascular depression. It is
important that both respiration and cardiovascular function is monitored for both
rate and character. Respiratory arrest should be treated by assisted ventilation,
preferably with oxygen supplementation. Maintain a patent airway and adequate
tissue oxygenation throughout the period of anaesthesia.
4.11
Withdrawal periods
Not to be used in animals intended for human consumption. Treated horses may
never be slaughtered for human consumption. The horse must have been
declared as not intended for human consumption under national horse passport
legislation.
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.