Chemical Immobilization of Wildlife Using the BAM Formulation
Wildlife practice is an extremely specialized area of veterinary medicine, and restraint nearly always requires the use of anesthetic drugs to allow a safe and efficient immobilization before the practitioner proceeds with plans for the targeted individual. Preventive medicine, surgery, imaging and anesthesia itself are key areas of the interventions carried out on the wildlife.
Each time an individual animal is immobilized, various procedures may be performed (e.g., weighing, measuring, ear-tagging, microchip implanting, vaccinations, de-worming, blood and hair collection for DNA testing) to take advantage of the immobilization. Thus, wildlife veterinary medicine is closely associated with anesthesiology due to the nature of wild animals and because the vast majority of interventions require the anesthetic immobilization of individuals.
History
Since the refinement of modern chemical immobilization techniques for wildlife began in the 1950s, the related drug protocols have undergone myriad changes and improvements. Early on, the basic techniques mimicked those used for thousands of years by indigenous tribes that had employed darts bearing tranquilizing plant extracts delivered via blow guns for the purposes of hunting. For the purposes of study and conservation however, modern researchers, veterinarians and wildlife managers required far safer drug formulations from which animals could reliably recover.
Much of the trial-and-error process began to take place in South Africa and other southern African nations in the 1950s and 1960s, and was conducted by wildlife managers. Thus, South Africa remains one of the countries where the practice of veterinary medicine in the wildlife realm is very advanced. National parks, private reserves and game farms regularly team up with wildlife allow the veterinarians to develop and improve techniques used to immobilize free-ranging animals. The veterinary practitioners involved in these procedures develop a particular knowledge and experience due to the existing biodiversity of species and the variety of conditions to which the animals are exposed.
In wildlife veterinary medicine, it is generally understood that the ideal immobilizing drugs for wildlife interventions must provide:
- Versatility (able to be used in different species)
- High potency in a small volume
- Wide margin of safety
- Quick and smooth induction and recovery
- Reversibility
- Rapid elimination from the body
- Minimal side effects
- Minimal handling risk
- Stability
- Analgesia
Varieties of Drugs Used in Wildlife Chemical Immobilization
Opiates have been widely applied in the chemical immobilization of wildlife from the beginning, largely due to their availability. Etorphine hydrochloride is a semi-synthetic opiate derivative which has up to 10,000 times the analgesic potency of morphine1 and is still widely used today. One advantage to opiates is that they provide analgesia as well as tranquilization; a disadvantage to opiates alone is that they can result in cardiac and an inordinate degree of respiratory depression at higher dosages.
Over time, drug combinations and formulations came to be understood as being safer and more efficacious than single agent immobilizing drugs. Tranquilizers such as acepromazine are often used in the field, as they produce a marked calming effect in animals. Unfortunately, tranquilizers cannot completely immobilize animals, and must be used in combination with other drugs to increase potency. Alpha-2 adrenergic agonist sedatives such as xylazine became popular in wildlife immobilization as well as being widely used in small animal veterinary clinics in domestic settings.2 These drugs also produce analgesia, but can also cause depression of nervous system in higher dosages.
Ketamine is probably the most commonly used injectable anesthetic used in veterinary medicine. However, ketamine cannot be used as a sole agent. In most cases, Ketamine is used in combination with other injectable agents (e.g., α2 agonists or benzodiazepines) to reduce or eliminate the less desirable side effects it carries when used alone. That said, ketamine has a wide margin of safety in most species and a residual analgesic effect following anesthetic recovery. Disadvantages include that ketamine alone does not provide muscle relaxation and muscle spasms may be observed. Further, its anesthetic effect may be limited depending on the species, and it necessitates a longer recovery as compared to gas anesthetics. In the U.S., ketamine is a Class III controlled substance.
The BAM Formulation for Wildlife
Chemical immobilization facilitates the capture and handling of many species of free-ranging animals. The relatively new combination of butorphanol tartrate, azaperone tartrate, and medetomidine HCl (or “BAM”) is being increasingly used to immobilize a variety of species.2 The three components of this drug combination appear to act synergistically to effect sedation sufficient for handling.1 Among those three components, medetomidine appears to be the principal driver of immobilization.
Butorphanol (butorphanol tartrate) is a synthetically derived opioid agonist-antagonist analgesic with a potency of about four to seven times that of morphine. In the United States, it is a U.S. Drug Enforcement Administration (DEA) class IV controlled substance.
The risk for physical dependence appears minimal in veterinary patients. Butorphanol is well-distributed, with the highest levels (of the parent compound and metabolites) found in the liver, kidneys, and intestine.
Azaperone is a butyrophenone tranquilizer that causes tranquilization and sedation, antiemetic activity, reduced motor activity, and inhibition of CNS catecholamines.
The butyrophenones as a class cause tranquilization and sedation (sedation may be less than with the phenothiazines), antiemetic activity, reduced motor activity, and inhibition of CNS catecholamines (dopamine, norepinephrine). Azaperone appears to have minimal effects on respiration and may inhibit some of the respiratory depressant actions of general anesthetics.
Medetomidine (medetomidine hydrochloride), is an α-2-adrenoreceptor agonist with sedative and analgesic properties. It is used by veterinarians as both a surgical anesthetic and analgesic. The pharmacological restraint and pain relief provided by medetomidine facilitates handling and aids in the conduct of diagnostic or therapeutic procedures.
The BAM formulation is known to provide a low-volume, reversible alternative to other immobilizing drug combinations and has been widely evaluated in studies for the immobilization of numerous wildlife species.
1Wolfe, L. et. al. Efficacy of a Low-Dosage Combination of Butorphanol, Azaperone, and Medetomidine (BAM) to Immobilize Rocky Mountain Elk. J Wildl Dis (2014) 50 (3): 676–680.
2Mich P.M., et. al. Evaluation of intramuscular butorphanol, azaperone, and medetomidine and nasal oxygen insufflation for the chemical immobilization of white-tailed deer, Odocoileus virginianus. J Zoo Wildl Med. 2008 Sep;39(3):480-7.
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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