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MONTH: December 2006

How to do pre-euthanasia sedation


Further to the discussion in your October article "Could carbon monoxide gas chambers make a comeback," I thought I'd wade in on pre-euthanasia sedation.

There is often confusion of terminology. The word "tranquilizer" and its verb form "tranq" are used generically. Same with the word "sedation" and "sedate."

Here's what's what:

Tranquilizer usually means phenothiazine-type drugs such as acepromazine. Tranquilizers reduce alertness and increase tolerance. They also reduce inhibition and blood pressure and lower the seizure threshold in some species. Acepromazine is label approved for dogs, cats and horses.
I do not recommend acepromazine as a pre-euthanasia drug due to its generally poor effect. A dangerous dog or cat is still conscious, therefore still dangerous. For friendly dogs, there is no need to administer acepromazine, as there is no anxiety issue.

According to the one and only study on carbon dioxide euthanasia, acepromazine is recommended for dogs being put to death in carbon dioxide chambers. It was found to reduce anxiety response in a significant percentage of dogs.

Sedatives reduce alertness by producing sleepiness. A typical sedative is xylazine, also used as a short-term analgesic and muscle relaxant. Brand names include "Rompun" and "AnaSed." These are label-approved for dogs and cats, at 20 mg/ml concentration, and for horses, deer, and elk at 100 mg/ml concentration. Adverse effects in dogs and cats include vomiting, reduced blood pressure, and lowered inhibition.

I do not recommend xylazine as a pre-euthanasia drug due to its generally poor effect. A dangerous dog or cat is still dangerous, even if sleepy and muscle relaxed, and the reduction in blood pressure is significant, a problem when trying to inject intravenously. For friendly dogs, there is no need to administer xylazine as there is no anxiety issue.

Anesthesia means loss of sensation, usually loss of consciousness brought about by the administration of an anesthetic. To be anesthetized literally means to have no feeling.

The best pre-euthanasia drugs are anesthetics. Most common and cost-effective is PreMix (5:1 ketamine-xylazine), dosed at 0.5-0.6 ml per ten pounds. An anesthetized dog or cat is unconscious, and therefore safe to handle. Adverse effects can be seizures or vomiting. PreMix is a veterinary compound in use since the mid-1970s, and is not an FDA approved drug.

Another pre-euthanasia anesthetic is Telazol (tiletamine-zolazepam), an FDA-approved drug similar in action to PreMix. Telazol is label-approved for dogs and cats and is, like PreMix, an effective pre-euthanasia drug when dosed at 0.3-0.6 ml per ten pounds.

There is a fallacy that best practice is to anesthetize all animals prior to euthanasia. This is simply not so. Best practice is to administer pre-euthanasia anesthetics when safety or technical difficulty issues arise. An intramuscular injection of a stinging medicine, such as either PreMix or Telazol, is in my opinion counterproductive unless needed.

The use of IV catheters for guardian-present euthanasia is becoming more prevalent in animal shelters, as well as in private veterinary practice. I mention their use in my euthanasia-by-injection classes.

I have been euthanizing feral cats for years, and believe that PreMix or Telazol first is the way to go. Then, when they are deep enough that they have a negative pinch-withdraw reflex, I administer the sodium pentobarbital via intracardiac injection, except for pregnant cats. Then I go IV.
I have also euthanized friendly cats, more than I can count unfortunately, and am a total fan of intraperitoneal. They never stop purring through the entire process, only stopping when they lose consciousness.

--Doug Fakkema
Animal Care &
Control Consultant
18 Hillcreek Blvd
Charleston, SC 29412



More about pre-euthanasia sedation of cats

For euthanasia pre-sedation, we use telazol, which combines tiletamine hydrochloride 50 mg/mL, and zolazepam hydrochloride 50. Tiletamine is similar to ketamine, and zolazepam is similar to diazepam (Valium). The tiletamine stings a bit, the only downside. Tiletamine and ketamine are dissociative anesthetics, but don't relax muscles. The zolazepam produces comfortable muscle relaxation and, with the tiletamine, combines to produce moderate anesthesia and very significant sedation.

The reason we like this combination is that, unlike with xylazine, the blood pressure doesn't plummet. Low blood pressure makes finding a vein very tough sometimes.

I also find that with telazol, I see much less twitching, and less agonal breathing in cats. The twitching and gasping breaths are spinal reflexes, and don't represent pain, but sure are disconcerting for the humans. In five years, I have seen two cats become twitchy or agitated with telazol. One was actually a serval, so who knows? The other was a very ill cat. The excitement lasted only a few seconds.

Considering how many euthanasias we do, it is hard to imagine a lower rate of complication. Technical information about telazol can be verified at <>. This is a very good site on animal anesthesia, and I use it all the time.

Telezol is much better for cats than dogs. I wouldn't use it with dogs, based on what others have told me.

Some people insist that the only way to euthanize is with an IV catheter in place. We find that the telazol produces comfortable sedation and such good anesthesia that cats never notice the second IV injection. To put in a catheter requires restraint, and while catheters are usually not painful, that is not always true. The telazol/euthanasia solution combination allows people to be with their cat for the entire process, and fussing with the catheter is avoided.

I was aghast to learn how executions by lethal injection are carried out. Apparently they use a paralytic agent, so if the condemned person is under-sedated, the person could be conscious for what is essentially a heart attack, chemically-induced with potassium chloride, or suffocation, because of inability to breathe. Also, the IV catheters used for human executions are not put in by experts, and the drugs can easily precipitate if they are accidently mixed. We do better, much better for our dogs and cats.

--Katherine Schubert, DVM
Cats Exclusive
Veterinary Center
19203 Aurora Ave. N.
Shoreline, WA 98133