Atracurium Besylate — Veterinary Vademecum Drug Reference

Dosage & Administration Guidelines

Species	Route	Dose	Frequency	Duration & Clinical Notes
Dog	IV	0.1-0.2 mg/kg (initial)	Initial bolus; maintenance: 0.05-0.1 mg/kg every 20-30 min as needed	Duration: As needed during anesthesia Notes: Administer slowly over 1-2 minutes to minimize histamine release. Use with adequate anesthesia.
Cat	IV	0.1-0.2 mg/kg (initial)	Initial bolus; maintenance: 0.05-0.1 mg/kg every 20-30 min as needed	Duration: As needed during anesthesia Notes: Cats may be more sensitive to histamine release; administer slowly.
Horse	IV	0.05-0.1 mg/kg (initial)	Initial bolus; maintenance: 0.02-0.05 mg/kg every 20-30 min as needed	Duration: As needed during anesthesia Notes: Use with caution in horses due to potential for histamine release and cardiovascular effects.
Cattle	IV	0.05-0.1 mg/kg (initial)	Initial bolus; maintenance: 0.02-0.05 mg/kg every 20-30 min as needed	Duration: As needed during anesthesia Notes: Not commonly used; ensure adequate ventilation support.
Small Ruminants (sheep, goats)	IV	0.05-0.1 mg/kg (initial)	Initial bolus; maintenance: 0.02-0.05 mg/kg every 20-30 min as needed	Duration: As needed during anesthesia Notes: Use with caution; monitor for respiratory depression.
Rabbit	IV	0.1-0.2 mg/kg (initial)	Initial bolus; maintenance: 0.05-0.1 mg/kg every 20-30 min as needed	Duration: As needed during anesthesia Notes: Rabbits are sensitive to respiratory depression; ensure mechanical ventilation.
Birds/Poultry	IV	0.1-0.2 mg/kg (initial)	Initial bolus; maintenance: 0.05-0.1 mg/kg every 20-30 min as needed	Duration: As needed during anesthesia Notes: Use with caution; birds have high metabolic rates and may require adjustments.
Exotic/Other	IV	0.1-0.2 mg/kg (initial)	Initial bolus; maintenance: 0.05-0.1 mg/kg every 20-30 min as needed	Duration: As needed during anesthesia Notes: Dose based on extrapolation; monitor closely.

Clinical Indications & Species Uses

General Indications

Adjunct to general anesthesia to provide muscle relaxation
Facilitation of endotracheal intubation
Facilitation of mechanical ventilation

Dog (Canine)

Adjunct to general anesthesia to provide skeletal muscle relaxation
Facilitation of endotracheal intubation
Facilitation of mechanical ventilation

Cat (Feline)

Adjunct to general anesthesia to provide skeletal muscle relaxation
Facilitation of endotracheal intubation
Facilitation of mechanical ventilation

Horse (Equine)

Adjunct to general anesthesia to provide skeletal muscle relaxation
Facilitation of endotracheal intubation
Facilitation of mechanical ventilation
Ophthalmic surgery requiring akinesia

Cattle (Bovine)

Adjunct to general anesthesia for surgical procedures
Facilitation of endotracheal intubation

Small Ruminants (Sheep / Goat)

Adjunct to general anesthesia for surgical procedures
Facilitation of endotracheal intubation

Rabbit & Small Mammals

Adjunct to general anesthesia for surgical procedures
Facilitation of endotracheal intubation

Avian & Poultry

Adjunct to general anesthesia for surgical procedures
Facilitation of endotracheal intubation

Exotic & Other Species

Adjunct to general anesthesia in various exotic species (e.g., reptiles, small mammals)

Pharmacology & Mechanism of Action

Drug Class: Neuromuscular blocking agent | Pharmacological Group: Non-depolarizing skeletal muscle relaxant

Mechanism of Action: Atracurium besylate is a non-depolarizing neuromuscular blocking agent that competitively binds to nicotinic acetylcholine receptors at the motor end-plate, preventing acetylcholine from binding and thereby blocking neuromuscular transmission. This results in skeletal muscle paralysis. The effect is reversible by acetylcholinesterase inhibitors (e.g., neostigmine) when the block is not profound.

Pharmacodynamics: Atracurium produces dose-dependent skeletal muscle relaxation. The onset and duration of action are influenced by dose and species. It has a moderate onset (1-3 minutes) and intermediate duration (20-40 minutes) in most species. It does not possess analgesic or anesthetic properties and must be used with adequate anesthesia/sedation. It causes minimal cardiovascular effects at clinical doses, but histamine release can occur, leading to hypotension, tachycardia, and bronchospasm, especially with rapid injection or high doses.

⚡ Pharmacokinetics Summary

Absorption: Not applicable for clinical use; atracurium is administered intravenously. Oral absorption is negligible and not used.

Distribution: Atracurium is widely distributed into extracellular fluid. It does not cross the blood-brain barrier or placenta in significant amounts. Volume of distribution is approximately 0.15-0.2 L/kg in dogs and cats.

Metabolism: Atracurium undergoes spontaneous degradation at physiological pH and temperature (Hofmann elimination) and ester hydrolysis by non-specific esterases. This metabolism is independent of hepatic and renal function, making it useful in patients with hepatic or renal impairment.

Excretion: Metabolites are excreted primarily in urine and bile. The parent drug is also excreted unchanged in urine and bile to a minor extent. The elimination half-life is approximately 20-30 minutes in dogs and cats.

Half-Life: Dogs: ~20-30 min; Cats: ~20-30 min; Horses: ~30-40 min; Humans: ~20 min

Bioavailability: Not applicable (IV only).

Protein Binding: Approximately 50% bound to plasma proteins.

Available Formulations & Strengths

Injectable Solution 10 mg/mL (2 mL, 5 mL, 10 mL vials) (IV)

Contraindications & Clinical Warnings

Contraindications:

Known hypersensitivity to atracurium or other bis-benzylisoquinolinium agents
Use in patients with inadequate ventilation support (unless mechanical ventilation is available)
Use in patients with myasthenia gravis (unless carefully managed)
Use in patients with severe electrolyte imbalances (e.g., hypokalemia, hypermagnesemia) that may potentiate neuromuscular blockade

Warnings & Clinical Precautions:

For IV use only; not for IM or SC administration
Should be administered by trained personnel with facilities for intubation, mechanical ventilation, and resuscitation
Monitor neuromuscular function (e.g., peripheral nerve stimulator) to avoid excessive dosing
Use with caution in patients with cardiovascular disease, asthma, or history of histamine release
May cause histamine release; administer slowly (over 1-2 minutes) and consider pretreatment with antihistamines if risk is high
Use with caution in neonates, geriatric patients, and debilitated animals
In food animals, observe withdrawal times; not approved for use in food animals in some countries
Store at 2-8°C; protect from light; do not freeze

Adverse Effects & Reactions

Common:

Hypotension
Tachycardia
Cutaneous flushing
Bronchospasm (especially in cats and horses)
Salivation

Serious / Severe:

Severe hypotension
Anaphylaxis
Prolonged neuromuscular blockade
Respiratory depression or apnea
Cardiac arrest (rare)

Rare:

Malignant hyperthermia (unlikely but possible in susceptible animals)
Myopathy
Seizures (due to metabolite laudanosine, especially in renal impairment)

Key Drug Interactions

Interacting Drug / Class	Clinical Effect & Mechanism	Severity
Inhalational anesthetics (e.g., isoflurane, sevoflurane)	Potentiate neuromuscular blockade; reduce atracurium dose by 20-30%	Moderate
Aminoglycoside antibiotics (e.g., gentamicin, amikacin)	May enhance neuromuscular blockade, leading to prolonged paralysis	High
Tetracyclines	May enhance neuromuscular blockade	Moderate
Magnesium sulfate	Potentiates neuromuscular blockade; use with caution	High
Calcium channel blockers	May potentiate neuromuscular blockade	Moderate
Diuretics (e.g., furosemide)	May cause electrolyte imbalances that alter neuromuscular blockade	Mild
Cholinesterase inhibitors (e.g., neostigmine, pyridostigmine)	Antagonize neuromuscular blockade; used for reversal	Moderate
Corticosteroids	May have variable effects; monitor	Mild

Overdose & Toxicity Management

Signs of Toxicity:

Prolonged muscle paralysis
Apnea
Severe hypotension
Bradycardia or tachycardia
Bronchospasm
Hypoxemia

Emergency Treatment Protocol: Maintain airway and provide mechanical ventilation until recovery. Administer anticholinesterase agents (e.g., neostigmine 0.04 mg/kg IV) after atropine (0.02-0.04 mg/kg IV) to reverse the block. Monitor vital signs and provide supportive care. In severe cases, consider administration of plasma expanders or vasopressors for hypotension. Laudanosine accumulation may cause seizures; treat with benzodiazepines if they occur.

Food Animal Withdrawal Times

Atracurium is not approved for use in food animals in many countries. If used in food animals, a prolonged withdrawal period (e.g., 30 days for meat and 7 days for milk) may be recommended based on clinical judgment, but no official tolerance has been established. Consult regulatory authorities.

Storage, Handling & Regulatory Information

Storage Temperature: 2-8°C (refrigerate)

Light Sensitivity: Light-sensitive — protect from direct exposure.

Handling & Special Conditions: Protect from light. Do not freeze. Use only if solution is clear and colorless. Discard unused portions after opening.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Not FDA-approved for veterinary use; approved for human use.

Extra-Label (Off-Label) Use: In the US, atracurium is not FDA-approved for veterinary species; use is extra-label under AMDUCA. It is a prescription drug for human use, and veterinary use requires a valid veterinarian-client-patient relationship. Extra-label use in food animals is subject to AMDUCA restrictions and requires extended withdrawal times.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Atracurium is a valuable neuromuscular blocking agent in veterinary anesthesia, particularly for procedures requiring profound muscle relaxation or controlled ventilation. Its unique metabolism (Hofmann elimination) makes it a good choice in patients with hepatic or renal impairment. However, it must be used with caution due to histamine release, especially in cats and horses. Always ensure adequate anesthesia and analgesia, as atracurium has no anesthetic or analgesic properties. Neuromuscular monitoring is recommended to avoid overdosing. Reversal with neostigmine and atropine should be performed only when the patient is starting to recover from the block. In emergency situations, rapid sequence intubation may be facilitated with atracurium, but only by experienced personnel. For food animals, consider regulatory restrictions and withdrawal times.

References & Literature

📚 Plumb's Veterinary Drug Handbook
📚 Papich Veterinary Pharmacology and Therapeutics
📚 Compendium of Veterinary Products (CVP)