Vetdrugs 2.0Isoflurane is a halogenated volatile anesthetic widely used for veterinary general anesthesia. Its relatively low blood solubility supports adjustment of anesthetic depth, and only a small fraction undergoes metabolism. It is used across companion-animal, equine, avian, reptile and laboratory-animal practice, commonly as part of a balanced anesthetic technique.
Group
Inhalational anaesthetic
Mechanism of Action
Isoflurane acts at multiple neuronal targets to produce reversible central nervous system depression. Enhancement of inhibitory GABA-A and glycine-receptor signaling, activation of some potassium channels and suppression of excitatory transmission contribute to unconsciousness and immobility. Brain and spinal-cord effects depend on the anesthetic partial pressure reaching those tissues, allowing depth to change as inhaled and tissue concentrations change.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Anaesthetic induction — Initial | Reference only | INHALATION | Inspired concentration up to approximately 5%, titrated to effect. | |
| Anaesthetic maintenance — Maintenance | Reference only | INHALATION | Inspired concentration approximately 1.5-2.5%, titrated to depth. | |
| Alternative anaesthetic concentration | Reference only | INHALATION | 0.5-3% inhaled, adjusted to depth and fresh-gas flow. |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Anaesthetic induction — Initial | Reference only | INHALATION | Inspired concentration up to approximately 5%, titrated to effect. | |
| Anaesthetic maintenance — Maintenance | Reference only | INHALATION | Inspired concentration approximately 1.5-2.5%, titrated to depth. | |
| Alternative anaesthetic concentration | Reference only | INHALATION | 0.5-3% inhaled, adjusted to depth and fresh-gas flow. |
Horses
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Anaesthetic requirement | Reference only | INHALATION | Large-animal section describes 1.5-2%; this is a concentration reference, not a weight-based dose. |
Ferrets
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| General anaesthesia | Reference only | INHALATION | Non-rebreathing system: induction 2-3%, maintenance 0.25-2%. Ferret alternative after medetomidine 50-100 mcg/kg and optional atropine 0.05 mg/kg SC: isoflurane 3% induction, 1-2% maintenance; medetomidine may be antagonized with atipamezole 0.25 mg/kg SC. |
Mice
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| General anaesthesia | Reference only | INHALATION | Non-rebreathing system: induction 2-3%, maintenance 0.25-2%. Ferret alternative after medetomidine 50-100 mcg/kg and optional atropine 0.05 mg/kg SC: isoflurane 3% induction, 1-2% maintenance; medetomidine may be antagonized with atipamezole 0.25 mg/kg SC. |
Rats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| General anaesthesia | Reference only | INHALATION | Non-rebreathing system: induction 2-3%, maintenance 0.25-2%. Ferret alternative after medetomidine 50-100 mcg/kg and optional atropine 0.05 mg/kg SC: isoflurane 3% induction, 1-2% maintenance; medetomidine may be antagonized with atipamezole 0.25 mg/kg SC. |
Gerbils
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| General anaesthesia | Reference only | INHALATION | Non-rebreathing system: induction 2-3%, maintenance 0.25-2%. Ferret alternative after medetomidine 50-100 mcg/kg and optional atropine 0.05 mg/kg SC: isoflurane 3% induction, 1-2% maintenance; medetomidine may be antagonized with atipamezole 0.25 mg/kg SC. |
Hamsters
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| General anaesthesia | Reference only | INHALATION | Non-rebreathing system: induction 2-3%, maintenance 0.25-2%. Ferret alternative after medetomidine 50-100 mcg/kg and optional atropine 0.05 mg/kg SC: isoflurane 3% induction, 1-2% maintenance; medetomidine may be antagonized with atipamezole 0.25 mg/kg SC. |
Guinea pigs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| General anaesthesia | Reference only | INHALATION | Non-rebreathing system: induction 2-3%, maintenance 0.25-2%. Ferret alternative after medetomidine 50-100 mcg/kg and optional atropine 0.05 mg/kg SC: isoflurane 3% induction, 1-2% maintenance; medetomidine may be antagonized with atipamezole 0.25 mg/kg SC. |
Chinchillas
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| General anaesthesia | Reference only | INHALATION | Non-rebreathing system: induction 2-3%, maintenance 0.25-2%. Ferret alternative after medetomidine 50-100 mcg/kg and optional atropine 0.05 mg/kg SC: isoflurane 3% induction, 1-2% maintenance; medetomidine may be antagonized with atipamezole 0.25 mg/kg SC. |
Reptiles
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| General anaesthesia | Reference only | INHALATION | Induction 5% with oxygen; maintain warmth and assess species-specific ventilation. Maintenance alternatives are 3-5% alone or 1.5-3% in a balanced technique. Ketamine 10-20 mg/kg IM or SC can shorten induction. Intubation and assisted ventilation may be needed; apnoea requires cessation/reduction of inhalant and ventilatory support. |
Birds
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| General anaesthesia | Reference only | INHALATION | Induction 3-5% with oxygen, then maintenance 1.5-2%; small-bird induction at 4% is another description. Recovery depends on duration and ventilation. |
Indications
- Maintenance of general anesthesia during surgery or diagnostic procedures in dogs, cats, horses and other veterinary species.
- Inhalational induction of anesthesia in selected birds, reptiles, small mammals or other suitable veterinary patients.
Contraindications
- Inability to control ventilation and monitor cardiac function
- Previous malignant hyperthermia; use cautiously with myasthenia gravis or elevated intracranial pressure.
Interactions
- Other anaesthetics and sedatives reduce the inhaled requirement.
Adverse effects
- Cardiovascular and respiratory depression
- Hypotension
Toxicity
Excess concentration requires reduction or cessation of delivery and cardiorespiratory support.
Monitoring and Administration
Use an isoflurane-calibrated vaporizer, oxygen and scavenging.
Monitor ventilation, oxygenation, blood pressure, heart rate and rhythm and anaesthetic depth.
MAC values are approximately 1.63% in cats, 1.3% in dogs and 1.31% in horses. Store tightly sealed and protected from light.
Isoflurane is supplied as volatile liquid in a 100 mL bottle.