Xylazine Hydrochloride
Dosage & Administration Guidelines
| Species | Route | Dose | Frequency | Duration & Clinical Notes |
|---|---|---|---|---|
| Dog | IM or IV | 0.5-2 mg/kg (IM); 0.1-0.5 mg/kg (IV) | Single dose; may be repeated at reduced dose if needed | Duration: Sedation lasts 30-60 minutes; analgesia 15-30 minutes Notes: Lower doses for sedation, higher for analgesia. Use with caution in debilitated animals. Atropine may be used to prevent bradycardia. |
| Cat | IM or SC | 0.5-2 mg/kg (IM); 0.1-0.5 mg/kg (IV) | Single dose; may be repeated at reduced dose if needed | Duration: Sedation lasts 30-60 minutes; analgesia 15-30 minutes Notes: Cats are sensitive to emetic effects. Use with caution in cats with heart disease. |
| Horse | IV or IM | 0.3-1.1 mg/kg (IV); 1-2 mg/kg (IM) | Single dose; may be repeated at reduced dose if needed | Duration: Sedation lasts 30-60 minutes; analgesia 15-30 minutes Notes: IV administration preferred for rapid effect. Avoid in horses with cardiac disease or respiratory compromise. |
| Cattle | IM or IV | 0.05-0.3 mg/kg (IM); 0.01-0.05 mg/kg (IV) | Single dose; may be repeated at reduced dose if needed | Duration: Sedation lasts 30-60 minutes; analgesia 15-30 minutes Notes: Cattle are highly sensitive; use low doses. May cause recumbency and bloat. Avoid in late pregnancy. |
| Sheep and Goats | IM or IV | 0.05-0.3 mg/kg (IM); 0.01-0.05 mg/kg (IV) | Single dose; may be repeated at reduced dose if needed | Duration: Sedation lasts 30-60 minutes; analgesia 15-30 minutes Notes: Similar to cattle; use low doses. Monitor for respiratory depression. |
| Rabbit | IM or SC | 1-5 mg/kg (IM) | Single dose | Duration: Sedation lasts 30-60 minutes Notes: Use with caution; rabbits are prone to respiratory depression. Often combined with ketamine. |
| Birds | IM | 1-10 mg/kg (IM) | Single dose | Duration: Sedation lasts 20-40 minutes Notes: Dose varies widely among species. Use with caution; monitor respiratory rate. |
Clinical Indications & Species Uses
- Sedation
- Analgesia
- Muscle relaxation
- Preanesthetic medication
- Chemical restraint
- Sedation
- Analgesia
- Preanesthetic medication
- Muscle relaxation
- Emetic (at low doses)
- Sedation
- Analgesia
- Preanesthetic medication
- Muscle relaxation
- Emetic (at low doses)
- Sedation
- Analgesia
- Preanesthetic medication
- Muscle relaxation
- Standing restraint for minor procedures
- Sedation
- Analgesia
- Preanesthetic medication
- Muscle relaxation
- Obstetrical procedures
- Sedation
- Analgesia
- Preanesthetic medication
- Muscle relaxation
- Sedation
- Analgesia
- Preanesthetic medication
- Sedation
- Analgesia
- Preanesthetic medication
- Sedation
- Analgesia
- Preanesthetic medication in various exotic species (e.g., reptiles, wildlife)
Pharmacology & Mechanism of Action
Drug Class: Alpha-2 adrenergic agonist | Pharmacological Group: Sedative, analgesic, muscle relaxant
Mechanism of Action: Xylazine is a potent alpha-2 adrenergic agonist that acts centrally and peripherally. It stimulates alpha-2 receptors in the central nervous system, leading to decreased release of norepinephrine and dopamine, resulting in sedation, analgesia, and muscle relaxation. It also activates peripheral alpha-2 receptors causing vasoconstriction and transient hypertension followed by hypotension. Its analgesic effects are mediated via activation of descending inhibitory pathways in the spinal cord and brainstem.
Pharmacodynamics: Xylazine produces dose-dependent sedation, analgesia, and muscle relaxation. It induces a state of recumbency in large animals and profound sedation in small animals. It also causes bradycardia, decreased cardiac output, and respiratory depression. It has emetic effects in cats and occasionally in dogs. It reduces gastrointestinal motility and can cause hyperglycemia by inhibiting insulin release. The duration of effects varies by species, with cattle being particularly sensitive.
β‘ Pharmacokinetics Summary
Available Formulations & Strengths
Contraindications & Clinical Warnings
- Known hypersensitivity to xylazine or other alpha-2 agonists
- Severe cardiac disease, arrhythmias, or hypotension
- Respiratory distress or severe respiratory disease
- Hepatic or renal insufficiency
- Shock or debilitated animals
- Late pregnancy (especially in cattle) due to risk of abortion
- Use with caution in animals with a history of seizures
- Should be used with caution in animals with pre-existing cardiovascular, respiratory, or hepatic disease.
- May cause bradycardia and hypotension; monitor vital signs closely.
- In cattle, xylazine can cause bloat and regurgitation; fasting before use is recommended.
- In horses, may cause sweating, piloerection, and ataxia; ensure a safe environment.
- In cats, may cause vomiting; use with caution in cats with respiratory disease.
- Avoid extra-label use in food animals without proper withdrawal times.
- Use with caution in very young, old, or debilitated animals.
- Have reversal agents (e.g., yohimbine, atipamezole) available.
Adverse Effects & Reactions
Common:
- Bradycardia
- Hypotension
- Respiratory depression
- Sedation
- Ataxia
- Vomiting (especially in cats)
- Hyperglycemia
- Diuresis
- Muscle tremors
Serious / Severe:
- Cardiac arrhythmias
- Severe hypotension
- Respiratory arrest
- Pulmonary edema (rare)
- Abortion in pregnant animals
- Seizures (rare)
- Prolonged sedation
Rare:
- Paradoxical excitation
- Allergic reactions
- Hepatotoxicity (with chronic use)
- Renal damage (with prolonged hypotension)
Key Drug Interactions
| Interacting Drug / Class | Clinical Effect & Mechanism | Severity |
|---|---|---|
| Other CNS depressants (barbiturates, opioids, anesthetics) | Additive sedation and respiratory depression; reduce doses of both agents. | High |
| Atropine or other anticholinergics | May prevent bradycardia but can cause tachycardia and hypertension. | Moderate |
| Epinephrine or other sympathomimetics | May cause severe hypertension and arrhythmias. | High |
| Tricyclic antidepressants | May potentiate cardiovascular effects. | Moderate |
| Beta-blockers | May cause severe bradycardia and hypotension. | High |
| Yohimbine or atipamezole | Reversal of xylazine effects; use for overdose or to shorten recovery. | Moderate |
Overdose & Toxicity Management
Signs of Toxicity:
- Severe bradycardia
- Hypotension
- Respiratory depression or arrest
- Hypothermia
- Prolonged sedation
- Coma
- Pulmonary edema
- Cardiac arrest
Emergency Treatment Protocol: Administer alpha-2 antagonist (e.g., yohimbine 0.1 mg/kg IV in dogs, 0.05-0.1 mg/kg IV in cats; atipamezole 0.05-0.1 mg/kg IV or IM). Provide supportive care: IV fluids, oxygen, thermoregulation, and monitoring of cardiac and respiratory function. In severe cases, mechanical ventilation may be necessary.
Food Animal Withdrawal Times
Withdrawal times vary by country and formulation. In the US, xylazine is not approved for food animals, but extra-label use requires extended withdrawal periods (e.g., 5 days meat, 3 days milk). Consult regulatory guidelines.
Storage, Handling & Regulatory Information
Storage Temperature: Store at controlled room temperature 20-25Β°C (68-77Β°F), protect from light.
Light Sensitivity: Light-sensitive β protect from direct exposure.
Handling & Special Conditions: Keep container tightly closed. Do not freeze. Use only if solution is clear and colorless.
Dispensing Status: Prescription Required (Rx Only)
Approval Status: Approved for veterinary use in dogs, cats, horses, and cattle.
Extra-Label (Off-Label) Use: In the US, xylazine is approved for use in dogs, cats, horses, and cattle. Extra-label use in other species or at different doses is permitted under AMDUCA, but requires a valid veterinarian-client-patient relationship and extended withdrawal times for food animals.
Clinical Pearls & Practice Notes
References & Literature
- π Plumb's Veterinary Drug Handbook
- π Papich Veterinary Pharmacology and Therapeutics
- π Compendium of Veterinary Products (CVP)