Yohimbine hydrochloride
Applications in Veterinary Medicine and Wildlife Management
Yohimbine hydrochloride is an alpha-two antagonist used for the reversal of the sedative effects of xylazine. It provides for a safe and rapid reversal (2-10 minutes) in animals in an easily administered low-volume dose.
General Information and History
Yohimbine is the principal alkaloid of the bark of the West African tree Pausinylstalia
yohimbine Pierre (formerly Corynanthe yohimbe). It first appeared in the veterinary text books in 1890 and was investigated in the 1960s for its potential as a human anesthetic. In the late 1980s, veterinary anesthesiologists began to assess the efficacy of yohimbine
to reverse xylazine in domestic species. Yohimbine hydrochloride was approved by the FDA in 1992 for use in dogs by Lloyd Laboratories under the trade name Yobine. In
1993 Wildlife Pharmaceuticals received FDA approval for Antagonil (Yohimbine
hydrochloride) for use in Cervidae.
Use in Wildlife Management
Yohimbine was first used successfully in members of the family Cervidae – elk and deer, free-ranging and confined. It has also been used to reverse xylazine in other non-
domestic hoof stock with consistent predictable results varying species by species. While it may be highly effective in reversing xylazine sedation in bighorn sheep, it may produce inconsistent erratic results in other members of the family Bovidae, including certain African antelope. It has consistently reversed xylazine sedation in non-domestic members of the families Canidae and Felidae.
It has been anecdotally reported that animals that are imprinted on humans and/or that are highly tame have been refractory to the reversal effects of yohimbine on xylazine sedation.
Use in Domestic Species
One of the first alpha-two antagonists developed to provide complete reversal of anesthetic effects of xylazine hydrochloride, yohimbine is predominantly used in
dogs.
Pharmacology and Chemistry
Yohimbine hydrochloride is a synthetic indole alkaloid. It is a selective competitive
alpha-two-adrenergic receptor antagonist. The reversal of the sedative effects of xylazine by yohimbine is rapid, usually 2-10 minutes. Yohimbine also reverses any cardiac
side-effects, such as arrhythmia and bradycardia, which may occur when xylazine is
administered alone.
The chemical name of yohimbine hydrochloride is 17ά-hydroxy-yohimban-16ά -
carboxylic acid methyl ester hydrochloride.
Pharmacokinetics
Yohimbine easily penetrates the blood brain barrier to block and antagonize the central
nervous system depression or sedation brought on by xylazine, a potent sedative and
analgesic with muscle relaxant properties. The CNS depressant effect and other pharmacologic effects are dose dependent.
CONTRAINDICATIONS AND PRECAUTIONS
Intrathoracic, intra-abdominal, subcutaneous or intramuscular injection is to be
avoided. When using yohimbine hydrochloride in wild or exotic species, one must
be prepared and knowledgeable regarding proper procedures to handle problems
resulting from animals being in lateral and sternal recumbency for extended
periods of time.
WARNING:
Do NOT use 30 days before or during the hunting season. Do NOT use in domestic food-producing animals.
ADVERSE REACTION
Hypotension and transient excitement were observed in clinical studies withyohimbine hydrochloride.
RECOMMENDED DOSE RANGE
The general guideline for yohimbine doses to reverse xylazine is 0.2-0.3 mg/kg body weight for cervids. For other species, please refer to the Handbook of Wildlife Chemical Immobilization (Kreeger et al.) available from Wildlife Pharmaceuticals Inc.
ADMINISTRATION
Yohimbine hydrochloride is administered intravenously at a dose of 0.2-0.3 mg/kg
body weight.
FDA Approved Presentation for Yohimbine hydrochloride
Yohimbine hydrochloride was approved by the FDA in a 2mg/ml and 5mg/ml strengths.
Compounded Forms Possible
5mg/ml and 10mg/ml yohimbine hydrochloride are standard concentrations compounded.
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