Yohimbine

Yohimbine is an alpha2-adrenergic antagonist used principally to reverse xylazine-induced sedation and associated physiologic effects. Its veterinary history predates more selective antagonists. Applications extend to selected other alpha2 agonists and amitraz intoxication, although the degree of reversal depends on the agonist, species and clinical context.

Group

Alpha2-adrenergic antagonist

Mechanism of Action

Yohimbine antagonizes alpha2-adrenoceptors and reduces the receptor-mediated inhibition of norepinephrine release caused by alpha2 agonists. Restoration of central noradrenergic activity promotes arousal and reverses part of the sedative and autonomic response. Peripheral receptor antagonism contributes to cardiovascular and metabolic reversal. Amitraz-associated effects may improve because its active compounds also stimulate alpha2 pathways.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Alpha2-agonist reversal	0.11 mg/kg	IV	Once	Titrate rather than automatically give the full amount.
Alpha2-agonist reversal	0.25–0.5 mg/kg	SC, IM	Once
Xylazine reversal	0.1 mg/kg	IV	Once	Slow injection.
Amitraz adverse-effect reversal	0.1 mg/kg	IV	As needed
Antiemetic use	0.25–0.5 mg/kg	SC, IM	Every 12 h

Cats

Use / stage	Dose	Route	Schedule	Instructions
Alpha2-agonist reversal	0.11 mg/kg	IV	Once	Titrate rather than automatically give the full amount.
Alpha2-agonist reversal	0.25–0.5 mg/kg	SC, IM	Once

Horses

Use / stage	Dose	Route	Schedule
Xylazine reversal	0.125 mg/kg	IV	Once
Detomidine reversal	0.2 mg/kg	IV	Once
Xylazine reversal alternative	0.075 mg/kg	IV

Cattle

Use / stage	Dose	Route	Schedule	Instructions
Alpha2-agonist reversal	0.125–0.2 mg/kg	IV	Once
Emergency xylazine reversal	0.1 mg/kg	IV

Sheep

Use / stage	Dose	Route	Schedule	Instructions
Alpha2-agonist reversal	0.125–0.2 mg/kg	IV	Once

Rabbits

Use / stage	Dose	Route	Schedule	Instructions
Alpha2-agonist reversal	0.2 mg/kg	IV	As needed

Mice

Use / stage	Dose	Route	Schedule	Instructions
Alpha2-agonist reversal	0.2 mg/kg	IP	As needed

Rats

Use / stage	Dose	Route	Schedule	Instructions
Alpha2-agonist reversal	0.2 mg/kg	IP	As needed

Birds

Use / stage	Dose	Route	Schedule	Instructions
Alpha2-agonist reversal	0.1 mg/kg	IV

Llamas

Use / stage	Dose	Route	Schedule	Instructions
Xylazine reversal	0.25 mg/kg	IV, IM

Indications

Reversal of xylazine-associated sedation and related effects in dogs.
Extra-label reversal of selected xylazine or other alpha2-agonist effects in horses and other veterinary species with a supported protocol.
Adjunctive reversal of clinically important alpha2-mediated effects in selected amitraz intoxications.

Contraindications

Do not use as an unrelated stand-alone equine disease treatment.

Interactions

Detomidine can increase yohimbine exposure; antagonizes alpha2 agonists.

Adverse effects

Excitation, tremor, exaggerated responses, tachycardia and high-dose seizures.

Toxicity

Excess can provoke tremor, seizures, tachycardia and agitation; monitor neurologic and cardiovascular status and provide supportive treatment.

Preparations

Preparation	Form	Strength	Route
Yohimbine injection 2 mg/mL	Injection	2 mg / mL	IV, IM, SC

Monitoring and Administration

Monitor heart rate and rhythm. A full dose may be unnecessary after sedative clearance: reported recommends one-third initially, followed if needed by equal increments every 5-10 minutes.

After ketamine or tiletamine-zolazepam combinations, allow dissociative effects to diminish before reversal to reduce rough recovery. IV reversal can wear off before IM xylazine, causing resedation. Amitraz combination report includes yohimbine 0.11 mg/kg IV or 0.25 mg/kg IM with atipamezole 50 mcg/kg IM; do not treat the combination as automatic routine reversal.