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Medications Used to Put Dogs to Sleep

Dog Euthanasia Drugs

The medications used to put dogs to sleep is something that may be of interest to dog owners who are considering putting their dogs down. Understanding the drug's mechanism of action can help them cope better considering that the topic of euthanasia is not commonly discussed thoroughly or extensively enough at veterinary appointments. This is often due to lack of time. Even when explanations are provided, dog owners may be looking for more in-depth information. This article aims to provide information about medications used to put dogs to sleep and their mode of action.

 Photo sample of an injection.

Photo sample of an injection.

Medications Used to Put Dogs to Sleep

Medications used to put dogs to sleep are controlled substances that can only be used by a veterinarian. The main drugs used to put a dog down are sodium pentobarbital used alone or in conjunction with phenytoin sodium. Both of these dog euthanasia drugs are meant to be administered intravenously.

Sodium pentobarbital is a short-acting barbiturate anesthetic drug, first introduced into veterinary medicine in 1931. When used for the purpose of euthanasia, it is given in an overdose amount. This drug works by producing anesthesia and rapid onset of unconsciousness.

Phenytoin sodium works by depressing the central nervous system, causing lowered blood pressure and cardiovascular collapse (by stopping the electrical activity of the heart). This drug's effect takes action during the deep anesthesia stage caused by the pentobarbital sodium.

Straight pentobarbital sodium for injection (Euthanasia) is available as Sleepaway (Fort Dodge), SP5 (Vedco), Socumb-6gr (Butler-Schein), Somlethol (Webster), SP6 (Vedco) and Fatal-PlusSolution (Vortec)

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Brand names of dog euthanasia drugs containing sodium pentobarbital and phenytoin sodium include “Euthasol” produced by Virbac, Beuthanasia-D Special produced by Schering-Plough, Euthanasia-III Solution produced by Med-Pharmex and Somnasol produced by Butler.

Did you know? In some states, sodium pentobarbital is sometimes utilized as a means of lethal injection in humans.

How do Medications To Put Dogs to Sleep Work?

Picture displayed for sample of injection only.

Picture displayed for sample of injection only.

The euthanasia solution is typically a bright color pink or blue so veterinarians can distinguish it from other drugs. The drug is typically injected into a vein in the dog's front leg.

As the drug goes into circulation, it firstly affects the cerebral cortex of the brain causing the dog to immediately become unconscious (as fast as 5 seconds) as if being anesthetized for a surgical procedure. Unconsciousness is defined as the state in which a dog lacks awareness and loses the ability for sensory perception, appearing to be in a deep sleep (hence the term "be put to sleep.")

Shortly afterward inducing the dog into a rapid coma-like state, respiratory depression, lowered blood pressure, lowered heart rate, and lowered body temperature follow and these effects lead to prompt induction of cardiac arrest. Cerebral death occurs prior to cessation of cardiac activity.

The whole process is very quick, taking only a few seconds, generally anywhere between 15 and 60 seconds. Often, dogs will drift into unconsciousness as the drug is still being injected.

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According to Plumb's Veterinary Drug Handbook, mild muscle twitching may occur after the injection. This twitching is normal and due to residual electrical impulses in the peripheral nerves. Sometimes, vocalizations, deep breaths or a terminal gasp, may also occur. These deep breaths are simply diaphragmatic reflexes. Veterinarians should warn owners about these possible reflexes. Dogs may also urinate or defecate.

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At times, when dogs have underlying severe cardiac or circulatory deficiencies, the action of euthanasia drugs may be delayed due to the impaired movement of the drug to its site of action (target organs). Occasionally, it may have happen that a dog manifests reflex responses with motor movement; however, dog owners must consider that the dog is unconscious and therefore does not experience pain, for the simple fact that the cerebral cortex is not functioning.

"In dogs that have very serious problems, especially diseases that cause widespread systemic disease (organ failure, heart disease, respiratory disease, systemic cancers), the body is already geared up to a higher level because it is fighting on many levels and it's those patients where I tend to see more pronounced movement and seemingly unsettled reactions to euthanasia. " Dr. Taylor, veterinarian

deep chest dog

The Two-Injection Method

Often, veterinarians will inject a larger than normal dose of sedative/anesthetic prior to injecting the pentobarbital. When veterinarians do this, it's called as the two-injection method. When this method is used, the drugs are often given IV for speed of action, but some drugs may be given into the muscle.

The sedatives chosen may vary between telazol, which is a mix of two drugs (tiletamine and zolazepam), ketamine (often combined with valium) propofol, Domitor, Acepromazine, xylazine.

In the past, the one-injection method was prevalent. Nowadays though, it may still be used in dogs that are already unconscious, comatose or anesthetized.

Many vets though prefer the two-injection method for a more peaceful-looking transition considering that sedatives or anesthetics given prior to the pentobarbital reduce the amount of muscle twitching normally seen after death and the appearance of what may be perceived as resistance/struggling by dog owners.

Once the sedatives are given, dogs will get drowsy and fall asleep. If dog owners wish to leave at this point, the animal won’t know the difference, explains veterinarian Dr. Dunn in the blog Diaries of a Veterinarian. If the owners decide to stay, most veterinarians will leave the owner and dog alone for a few last, precious minutes as they go into the back room and pull up the pink, thick euthanasia solution from the bottle. If the owners want more time, this is a good time for the vet to run several errands such as refilling prescriptions or checking on a patient's recovery.

Then, the final injection is given. Finding the vein in a very sick, debilitated and dehydrated dog can sometimes be a challenge. The thick solution is then injected and the dog often stops breathing even before the vet removes the needle. The vet then listens to the heart and once he/she assures there is lack of heartbeat, pronounces the dog dead. The euthanasia is now over and arrangements are next made for disposal of the corpse (burial, private cremation, communal cremation). Dogs bodies may be gone, but their memories are cherished forever.

For further reading:

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  • Case Reports in Emergency Medicine Volume 2016, Article ID 6270491, 4 page Pentobarbital Toxicity after Self-Administration of Euthasol Veterinary Euthanasia Medication Steven Jason Crellin and Kenneth D. Katz
  •  Plumb's Veterinary Drug Handbook 7th Edition By Blackwell Publishing

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