NOAH Compendium of Animal Medicines: Isoba 100% w/w inhalation vapour, liquid.

Isoba 100% w/w inhalation vapour, liquid.

Contra-indications, warnings, etc

This product should not be used in animals with a known sensitivity to isoflurane or a known susceptibility to malignant hyperthermia.

Isoflurane has little or no analgesic property. Adequate analgesia should always be given before surgery. The analgesic requirements of the patient should be considered before general anaesthesia is ended.

Reptiles may be difficult to induce with inhalation agents due to breath holding.

The metabolism in small mammals can be affected by decrease in body temperature, due to the high surface area to bodyweight ratio. Therefore body temperature should be monitored and kept stable.

Isoflurane causes dose-dependent respiratory depression and hypotension. Cardiac arrhythmias and transitory bradycardia have been reported rarely. In line with the known pharmacodynamic properties of this anaesthetic, including the reduction of systemic blood pressure, a risk-benefit assessment should be conducted before using this product in patients with compromised cardiovascular function.

Although isoflurane can be used during cranial surgery and in patients with head injuries, increased cerebral blood flow and intracranial pressure can occur. Hyperventilating the patient can reduce the increased intracranial pressure.

Malignant hyperthermia has been reported very rarely in susceptible animals.

Where no MAC/ED50 values are mentioned for the different species, use of isoflurane should only be considered following a risk/benefit assessment by the veterinary surgeon.

Isoflurane causes a dose-dependent reduction in systemic blood pressure.

Cardiac arrhythmias and transitory bradycardia have been reported rarely.

Skilled monitoring of anaesthetic depth should accompany isoflurane use. As the primary signs of overdose are due to cardiopulmonary depression, cardiovascular signs (e.g. pulse strength, heart rate, arterial blood pressure, mucous membrane colour and refill time) and respiratory signs (rate and depth of respiration) should be particularly noted.

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.

Respiratory arrest should be treated by assisted ventilation. In the case of cardiac arrest, perform a complete cardio pulmonary resuscitation.

Although isoflurane has been used safely during caesarean section in the dog and cat, no full data are available on its use during pregnancy and lactation in the target species. Use in pregnant and lactating animals should, therefore, only be considered following a risk/benefit assessment by the veterinary surgeon.

Interactions

Delivery in nitrous oxide and premedication with agents such as acepromazine, opioids, benzodiazepines and alpha-2-adrenoreceptor agonists are compatible with isoflurane use. However concurrent use of such agents, in particular the alpha-2-adrenoreceptor agonists, is expected to reduce the concentration of isoflurane necessary for induction and maintenance of anaesthesia.

Isoflurane may be degraded to carbon monoxide by dried carbon dioxide absorbents.

Incompatibilities

Carbon monoxide production from contact with desiccated soda- or baro-lime has been reported. This is avoided by ensuring that soda-lime is fresh or rehydrated if it has become desiccated.

Operator warnings

•Do not breathe vapour. Users should consult their relevant 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 breast-feeding women should avoid exposure to the product and should avoid operating rooms and recovery areas.

•Avoid using masking procedures for prolonged induction and maintenance of general anaesthesia. Use cuffed endotracheal intubation when possible for the administration of Isoba during maintenance of general anaesthesia.

•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.

•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 this leaflet.

•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: Ensure a patent airway and give symptomatic and supportive treatment. Note that adrenaline and catecholamines may cause cardiac dysrhythmias.

Withdrawal periods

Horse meat: 2 days.

Do not use in rabbits intended for human consumption.

Do not use in pigeons kept as food producing animals. Do not use in mares producing milk for human consumption.

For animal treatment only. Keep out of the reach and sight of children.