Lidocaine is a local anesthetic drug that can be administered to dogs and cats in high doses to achieve death. It requires pre-euthanasia anesthesia to induce unconsciousness beforehand and appears to lead to a smooth death in patients. Why use it? Pentobarbital and other euthanasia drugs may not be available and there are times when we need less hazardous drugs in the body (1,2). A recent 2025 study published in the American Journal of Veterinary Research (AJVR) provides us a nice opportunity to explore lidocaine as a euthanasia agent.

Euthanasia in companion animals is regularly achieved by injection of euthanasia drugs like pentobarbital sodium (most common), phenytoin sodium, T61, magnesium sulfate, and potassium chloride. The goal of these drugs is to rapidly induce death via their specific pharmacologic response in the body. For example, pentobarbital shuts down the central nervous system whereas potassium chloride stops the heart. 

Lidocaine is now proven to also facilitate death in companion animals like dogs and cats. Lidocaine has been used as a euthanasia agent in horses and livestock for many years (3), but while some veterinarians have used it in small animals, the data was lacking to show exactly how much to give and what death would look like in comparison to other drugs. Lidocaine induces lethal effects by blocking voltage-gated sodium channels from inside cells and preventing subsequent channel activation. Impulse conduction slows, the rate of rise and the magnitude of action potentials decrease, and the threshold for excitation is raised progressively until an action potential can no longer be generated.(4) The entire nervous system is made quiet and life ceases.

From a practical aspect, lidocaine is typically inexpensive and readily available. In the US, it is not labeled as a euthanasia agent by the FDA, however that does not void its use. It must only be given to anesthetized patients, making it less attractive perhaps than pentobarbital that can be given intravenously to awake patients. What the 2025 study shows us is that it meets many criteria listed in the AVMA’s Guidelines for the Euthanasia of Animals and that it causes permanent death.

How to Euthanize Dogs and Cats with Lidocaine
~ Intravenous (IV) and Intracardiac (IC) Routes
1. Induce unconsciousness.
2. Administer lidocaine 28 mg/kg rapidly.
3. Death is expected in less than 5 minutes.
4. If the heart keeps beating after 5 minutes, readminister.

~ Intrathecal (ITh) Route
1. Induce unconsciousness.
2. Lie the patient in lateral recumbency. Lay out your supplies near your planned injection site.
3. Insert spinal needle or catheter into the subarachnoid space (the atlanto-occipital junction may be easiest location).
4. Remove the same volume of cerebrospinal fluid as you will be injecting, a 1:1 ratio.
5. Administer lidocaine 4 mg/kg slowly and monitor for signs of life.
6. Death is expected in less than 10 minutes (5 minutes typical)
7. If the heart keeps beating after 10 minutes, readminister.

Expected Signs of Death with Lidocaine Euthanasia
~ IV and IC administration will lead to more active signs of death than the ITh route.
~ Active signs of death include large opisthotonus stretching, agonal breathing, mild abdominal peristaltic waves, and body “jolting”. The larger the animal, the more active their death appears to be.
~ ITh administration requires more skill and death takes longer, however active signs of death are reduced leading to a visually “quieter” euthanasia.

For dog and cat euthanasia appointments, lidocaine, and other local anesthetics like mepivacaine or bupivacaine, may be well suited when the use of controlled substances is not possible or when burial is chosen for bodycare. It is good to have alternatives to pentobarbital euthanasia, although pentobarbital will likely remain the leader in euthanasia drugs for a long time because of the ability to administer it intravenously in awake patients. The Companion Animal Euthanasia Training Academy (CAETA) is adding lidocaine euthanasia training to help veterinary practitioners understand the technique.

References

1. Cooney, K., & Titcombe, L. (2022). Lessons and Recommendations from a Pentobarbital Shortage: US and Canada 2021. Animals (Basel), 12(3), 365-. https://doi.org/10.3390/ani12030365

2. Hess, W., Kollias, N., Pikel, L., Johnson, C., Cornwell, E., Golab, G., Bright-Ponte, S., Bataller, N., & Murphy, M. (2023). Survey of veterinarians who use pentobarbital for euthanasia suggests knowledge gaps regarding animal disposal. Journal of the American Veterinary Medical Association, 261(11), 1707–1715. https://doi.org/10.2460/javma.23.03.0161

3. Aleman, M., Davis, E., Williams, D. C., Madigan, J. E., Smith, F., & Guedes, A. (2015). Electrophysiologic Study of a Method of Euthanasia Using Intrathecal Lidocaine Hydrochloride Administered during Intravenous Anesthesia in Horses. Journal of Veterinary Internal Medicine, 29(6), 1676–1682. https://doi.org/10.1111/jvim.13607

4. Cooney, K. A., Robertson, S. A., & Kogan, L. R. (2025). Euthanasia of canines and felines under anesthesia can be achieved with lidocaine or mepivacaine via intrathecal, intravenous, or intracardiac routes. American Journal of Veterinary Research, 1–6. https://doi.org/10.2460/ajvr.25.01.0013