Chemical Immobilization and Medication Dosage Chart for Bears

Capturing and chemically immobilizing a bear can be the most traumatic incident of its life, thus, it is extremely important to justify all capture and trapping procedures. Anyone involved in the chemical immobilization of bear or any wildlife should be trained accordingly. During chemical immobilization and capture operations, a wildlife veterinarian should be consulted and part of the team, whether the capture is for research or other purposes.¹ The handling of any captured bear should be performed in a careful manner and as expediently as possible to ensure that no trauma, behavioral distress, or unnecessary discomfort can occur.

In the U.S., federal regulations require that research facilities and entities, animal dealers and exhibitors have an attending veterinarian to consult and provide guidance on capture and chemical immobilization procedures and techniques.¹ The Food and Drug Administration (FDA) determines what immobilizing drugs can be used on certain species, including bear. The FDA also requires a registration certificate for those using controlled substances; these are obtained through the U.S. Drug Enforcement Agency (DEA). Personnel or field technicians who may be using or even administering controlled drugs must be working under the supervision of a certificate holder, which is often the consulting veterinarian. The certificate holder is also the party responsible for keeping detailed logs of drug use.² Some states also have veterinary codes in place which must be adhered to by those participating or engaging in the immobilization and capture of wild animals through chemical means.

Chemical Immobilization and Stress

In most situations, the capture and handling of wild bear imposes stress. This is a normal adaptive response in which the target animal must expend energy to cope with a threat to its welfare. When a threat is extreme or prolonged however, the stress response can have a damaging effect on bear’s health.² In such cases, energy is used at the expense of other biologic functions. The consequences of capture-related stress have implications for both the health of the target animal and the interpretation of research results. Understanding the physiologic responses to different methods of capture and handling enables for the appropriate selection of capture and immobilization methods, thus minimizing the length and degree of stress imposed on animals.¹

Bear Species of North America

Three species of bears live in North America: These are black bears, brown bears (e.g., Grizzlies), and polar bears.

The North American Black Bear (Ursus Americanus) is brown to black in color, and is the most common bear in North America. These range from the State of Florida north, into Canada and north to Alaska. The black bear is omnivorous, with a diet of mostly vegetable matter. Males reach full size at about eight years of age. Females mate and produce cubs at five to seven years of age. The males usually weigh up to 280kg (600 pounds), although they can occasionally weigh much more. Black bears often live up to 25 years in the wild; older bears have been documented however, the majority of bears seldom live longer than 25 years.

There are several subspecies of Brown Bear (Ursus Arctos), which can be found in Alaska, western Canada, and parts of the northwestern United States. Small populations are also known to exist throughout parts of Europe and Asia. Russia is also reported to have a population of brown bear. Brown bear range in color from almost black, brown to very light brown. Size varies greatly depending on geographic location and general food availability. The largest bears exist along the coast of Alaska and Russia, growing to sizes rivaling that of the Polar Bear. Bears of the North American Rocky Mountains (Grizzlies) tend to be smaller.

Polar Bears (Ursus Maritimus) are among the largest bears in the world, with adult males reaching up to 800 kg. (1760 lbs). These bears inhabit the areas in and around the Arctic Circle. In Canada, the largest male bear recorded weighed 654 kg (1439 lbs).² The average weight of male polar bears in Canada is about 500 kg (1100 lbs). Adult female polar bears are smaller and average around 300 kg (660 lbs).

Chemical Immobilizing Agents for Bear

Given the wide range of weight and physical characteristics of North American bears, obviously there is no one-size-fits-all protocol for their chemical immobilization.³ It is also important to note that no individual drug meets all of the safety requirements and level of effectiveness for all animals. Most drugs will be administered through intramuscular (IM) injection via remote delivery (darts and dart guns).⁴ An ideal drug or formulation will be in a high enough concentration that the risk for bruising and or muscle tearing during the liquid pressure injection is minimized.²

Some of the drugs used for the chemical immobilization of bear include:

Narcotic Analgesics

• Etorphine HCl – Antagonist: Naxolone Hydrochloride (HCl)
• Carfentanil citrate – Antagonist: Naxolone Hydrochloride (HCl)
• Thiofentanil A3080 – Antagonist: Naltrexone

Dissociative Anesthetics

• Ketamine Hydrochloride (HCl) “Ketaset” – Antagonist: Yohimbe Hydrochloride (HCl)

-Most versatile drug for animal immobilization and capture

-Often painful with injection

-Seizure can result when used alone

-Schedule III Drug

• Tiletamine Hydrochloride (HCl) and Zolazepam Hydrochloride (HCl) “Telazol or CI-744” – Antagonist: Doxapram Hydrochloride (HCl)

-2.5 times more potent than ketamine; wide safety margin

-Schedule III drug

Non-Narcotic Sedatives

• Xylazine Hydrochloride (HCl) – Antagonist: Yohimbe Hydrochloride (HCl)

-Ungulates highly sensitive

-Often induces vomiting

• Dexmedetomidine (Dexdomitor) – Antagonist: Atipamazole

-10-20 times more potent than xylazine

• Butorphanol

-Enhances xylazine effects and improves the quality of immobilization

-Ungulates and carnivores require higher dosages

Tranquilizers

• Acepromazine Maleate (Acepromazine) – Antagonist: None known
• Diazepam “Valium” – Antagonist: None known

Antagonists (reversal agents)

• Naxolone Hydrochloride (Naxolone or Narcan)
• Yohimbe Hydrochloride (Yohimbe)
• Doxapram Hydrochloride (Doxapram)
• Tolazoline
• Atipamazole (Antisedan)

The BAM formulation (consisting of Butorphanol, Azarperone and Medetomidine) is also suitable for the chemical immobilization of bear. BAM is effective in a wide variety of species and is known for a quick induction; antagonists provide smoother and more rapid recovery than ketamine or telazol combinations.²

Chemical Immobilization Dosage Charts for Bear

For the chemical immobilization of bear, Chemical Immobilization of Wild and Exotic Animals (Nielsen, 1999) recommends the following dosages and formulations:

For the administration of medetomidine+telazol for bear, the drug volume calculations recommended by the Province of Alberta, Canada are as follows:

Other drugs and drug formulations, as well as dosing recommendations can be found in Handbook of Wildlife Chemical Immobilization (Arnemo & Kreeger, 2018) and Chemical Immobilization of Wild and Exotic Animals (Nielsen, 1999).

¹Wolfe, L. et. al. Evaluation of Chemical Immobilization in Captive Black Bears (Ursus Americanus) Receiving a Combination of Nalbuphine, Medetomidine, and Azaperone. J Wildl Dis (2019) 55 (1): 84–90.

²Cattet, M, et. al. Physiologic Responses of Grizzly Bears to Different Methods of Capture. Journal of Wildlife Diseases, 39(3), 2003, pp. 649–654

³Arnemo, J., Kreeger, T. (2018). Handbook of Wildlife Chemical Immobilization 5th Ed. Sunquest Publishing, 2007, 432 pages.

⁴Nielsen, L. Chemical Immobilization of Wild and Exotic Animals. (1999) Ames, Iowa, Iowa State University Press.

About NexGen Pharmaceuticals

NexGen Pharmaceuticals is an industry-leading veterinary compounding pharmacy, offering sterile and non-sterile compounding services nationwide. Unlike other veterinary compounding pharmacies, NexGen focuses on drugs that are difficult to find or are no longer available due to manufacturer discontinuance or have yet to be offered commercially for veterinary applications, but which still serve a critical need for our customers. We also specialize in wildlife pharmaceuticals, including sedatives and their antagonists, offering many unique options to serve a wide array of zoo animal and wildlife immobilization and anesthesia requirements.

Our pharmacists are also encouraged to develop strong working relationships with our veterinarians in order to better care for veterinary patients. Such relationships foster an ever-increasing knowledge base upon which pharmacists and veterinarians can draw, making both significantly more effective in their professional roles.

Disclaimer

The information contained in this blog post is general in nature and is intended for use as an informational aid. It does not cover all possible uses, actions, precautions, side effects, or interactions of the medications shown, nor is the information intended as medical advice or diagnosis for individual health problems or for making an evaluation as to the risks and benefits of using a particular medication. You should consult your veterinarian about diagnosis and treatment of any health problems. Information and statements have not been evaluated by the Food and Drug Administration ("FDA"), nor has the FDA approved the medications to diagnose, cure or prevent disease. Medications compounded by NexGen Pharmaceuticals are prepared at the direction of a veterinarian. NexGen Pharmaceuticals compounded veterinary preparations are not intended for use in food and food-producing animals.

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