Special Update: Pentobarbital alternatives

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While pentobarbital shortages are lessening in some parts of the world, many are still without and seeking safe and reliable alternatives. Pentobarbital is the #1 go-to drug for animal euthanasia in many countries. It is reliable with consistent dosing, with minimal side effects leading to a peaceful death when performed properly. Proceeding without this familiar drug leaves many practitioners worried and unsure how best to accurately handle the alternatives as well as predict how the patient will respond. This special edition CAETA blog presents ways to both conserve pentobarbital solution for those who have it, and reliably lean on alternatives regardless of the patient type or the presence of witnesses.

Conserving Pentobarbital
To conserve pentobarbital euthanasia solution, a wise choice is to reduce how much is used. When euthanasia is warranted to end patient suffering, only using the recommended dose is called for. Many practitioners give a little extra to ensure death is complete, but it’s really not necessary. The intravenous (IV) dose for all companion animals is 85mg/kg (some exotic species like reptiles may require more). And while the Companion Animal Euthanasia Training Academy (CAETA) is an advocate for intraorgan injections as viable technique options, they do require more solution, sometimes triple the IV dose. In a time of shortage, IV administration will help to preserve what minimal drug reserves there are.

Alternative Euthanasia Drug Solutions
When working with alternatives, veterinarians and other practitioners may feel compelled to prepare witnesses for physiologic variations compared to pentobarbital-induced death. This is reasonable, however, detailed descriptions may not be necessary. Each of the following alternatives require patient unconsciousness before administration, therefore any and all active signs of death go unperceived by the patient. Depending on the alternative drug used and the administration rate, the patient may exhibit agonal breathing, muscle fasciculations, paddling, and opisthotonus stretching. CAETA recommends gently mentioning to owners/clients that some active signs of death such as mild body stretching and deep reflexive breaths may occur, but are very normal and natural. The animal remains pain-free and comfortable.

T61: For those countries still carrying T61, this drug is a reliable euthanasia solution. It is a combination of Embutramide, Mebezonium iodide, and Tetracaine hydrochloride. The solution is administered in unconscious animals via IV injection only. An indwelling IV catheter is advised. The dose is 0.3 mL per kg (0.14 mL/lb) body weight intravenously at a moderate rate. (1) The patient may exhibit muscle fasciculations, with cardiac arrest in under two minutes, at or near the same rate as a pentobarbital euthanasia. (2)

Potassium chloride (KCl): KCl can be purchased as a medical grade solution or it can be created. This is done by adding 350 grams of KCl salt to 1 liter of water to generate 350 mg/ml of saturated solution (mix frequently to reduce particulate matter from accumulating). (3) The intravenous KCl dose is 150 mg/kg or 2 mEq/kg (some literature shows half these doses effective). This equates, to be safe on the high side, to around 25mls for a 45 kg patient of a 350 mg/ml saturated solution or around 45 mls of a 2 mEq/ml pre-bottled solution. Having extra on hand is advisable. Cardiac arrest is fast, expected in under 2-3 minutes. Auscult the heart for as long as is necessary to ensure death is complete. Agonal breathing is possible along with muscle fasciculations. The solution is administered rapidly in unconscious animals via IV injection only. KCl induces cardiac arrest, considered to be highly stressing and painful in awake animals. Pre-euthanasia sedation protocols by themselves are not enough; anesthetic protocols must be used to induce unconsciousness. A colored dye can be added to the solution to identify it for euthanasia purposes.

Magnesium sulfate (MgSO4): MgSO4 has no specific dose that CAETA has found, although ranges exist from 750-1000 mg/kg via rapid IV administration. MgSO4 solution is either purchased as medical grade solution (500 mg/ml) or is created by dissolving 350g pure magnesium sulfate (epsom salts) in 1 liter of room temp water to saturation (particulate matter accumulating in the bag/bottle). (3) This solution is hard to work with in cold climates and it precipitates fast; mix repeatedly. Administer in unconscious patients until cardiac arrest is complete (anesthetize similar to KCl requirements). Physical effects of death can include minor body stretching, muscle fasciculations, and agonal breaths, with cardiac arrest in under 2 minutes. A colored dye can be added to the solution to identify it for euthanasia purposes.

Author’s Note: This author has personally euthanized pets using KCl and MgSO4 and heard reports from multiple colleagues sharing successes. This author has not used T61, but understands it to be highly effective and a reliable alternative to pentobarbital when necessary.

1. https://www.drugs.com/vet/t-61-euthanasia-solution-can.html
2. W V Lumb, K Doshi, R J Scott A comparative study of T-61 and pentobarbital for euthanasia of dogs. J Am Vet Med Assoc. 1978 Jan 15;172(2):149-52.
3. Callan R, Chappell J, Cooney K, et al. Veterinary Euthanasia Techniques; A practical guide. Wiley-Blackwell. Ames, IA. 2012.

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Dr. Kathleen Cooney

DVM, CHPV, CPEV, DACAW resident Founder, Senior Director of Education for the Companion Animal Euthanasia Training Academy

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