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For Equine Vets Everywhere

Euthanasia by lethal injection in the absence of Somulose®

With the potential interruption to Somulose® supply until mid-August 2019 we have provided guidance on the use of Pentobarbital for euthanasia.

A general review of equine euthanasia is provided here (including administration of Somulose®).


Two pentobarbital solutions are currently authorised in the UK and listed in the NOAH compendium for euthanasia of the horse:

  • Euthoxin® (Channelle) 500mg/ml
  • Euthasol Vet® (Dechra) 400mg/ml

The recommended dose of Euthoxin® (Channelle) 500mg/ml for a 500kg horse is 100ml

The recommended dose of Euthasol Vet® (Dechra) 400mg/ml for a 500kg horse is 175ml

Other pentobarbital solutions containing 200mg/ml - 500mg/ml are authorised for use in the horse, but these are not routinely sold in the UK.

Check the volume you require of the product that you use.

Pentobarbital is a schedule 3 drug, so specific drug recording is not required. Safe custody requirements are less restrictive than for schedule 2 drugs (although Somulose® is unique in being a Schedule 2 drug that does not have safe custody requirements).

Pentobarbital Protocol

Personal experience of this technique is that it is an effective and safe method of euthanasia under the following protocol, but it is observed that horses tend to move backwards during euthanasia.

  1. Place and secure an intravenous catheter into the jugular vein
  2. Add a long extension tube (50-100cm) so that injection can continue as the horse moves away from you/backwards during euthanasia
  3. Sedate the horse as for anaesthesia (20ug/kg of detomidine ie 1 ml for a 500kg horse)
  4. Draw up the multiple syringes required for the horse. Overestimate the volume!
  5. Once the horse is sedated and in a safe location administer the full dose required as quickly as is safely possible – continue injecting as the animal begins to be anaesthetised
  6. If necessary, continue to administer further pentobarbital solution until the horse dies.

Euthanasia of the Anaesthetised Horse

Euthanasia of horses that are already anaesthetised or that are anaesthetised via other means can be undertaken using Pentobarbital or using a concentrated solution of potassium chloride (if other methods are unavailable and if considered appropriate under the prescribing cascade).

Potassium Chloride Protocol


  • Sterile solutions are not required. Potassium Chloride powder/crystals can be dissolved in water (until the solution is fully saturated)
  • 100ml saturated solution is usually enough for a 500kg horse
  • Ensure safety of those around the horse; legs / muscles will move spontaneously due to muscle cell depolarisation - this can be dangerous and distressing to clients (who must be warned)
  • Administer by rapid IV injection until the heart stops