Drug Monograph
Full clinical overview, indications, dosage references & safety notes.
Overview
Atracurium (Tracrium®) is a nondepolarizing neuromuscular blocking agent used in dogs and cats as an adjunct to general anesthesia when complete skeletal muscle relaxation is required. It produces paralysis of striated muscles but provides no sedation or analgesia and therefore must never be used as a sole agent.
In dogs and cats, atracurium is most commonly administered intravenously after induction of general anesthesia to facilitate endotracheal intubation, optimize surgical conditions, and support controlled mechanical ventilation. It is also used to aid in central positioning of the globe during ophthalmic surgery under general anesthesia.
A unique clinical application in small animal practice is the intraurethral administration of atracurium in male cats with urethral obstruction, where it can assist with urethral plug removal. In both dogs and cats with urinary retention secondary to upper motor neuron dysfunction, intraurethral use has been shown to facilitate bladder expression without causing significant systemic neuromuscular blockade.
Mechanism of Action (MOA): Atracurium competitively binds to nicotinic acetylcholine receptors at the neuromuscular junction, preventing acetylcholine from activating the motor end plate. This results in reversible paralysis of skeletal muscles. Its neuromuscular blocking effects may be potentiated by certain inhalant anesthetics.
Atracurium has minimal cardiovascular effects at clinically recommended doses and is considered suitable for dogs and cats with renal or hepatic insufficiency because it is eliminated primarily through ester hydrolysis and Hofmann elimination, processes independent of liver and kidney function.
Indications
Atracurium is used in dogs and cats as an adjunct to general anesthesia to achieve controlled, reversible skeletal muscle paralysis. It is indicated only in fully anesthetized patients with secured airways and appropriate ventilatory support.
- Adjunct to general anesthesia (dogs and cats): Used to provide complete muscle relaxation during surgical procedures or to facilitate mechanical ventilation when spontaneous ventilation is inadequate or undesirable.
- Facilitation of endotracheal intubation (dogs and cats): Administered after induction of general anesthesia to ease endotracheal tube placement by reducing jaw tone and laryngeal reflexes.
- Ophthalmic surgery (dogs and cats): Used to assist with central positioning of the globe (bulbus) during ophthalmic procedures performed under general anesthesia.
- Urethral obstruction in male cats: Intraurethral administration may be used to facilitate removal of urethral plugs and improve success of obstruction relief.
- Urinary retention due to upper motor neuron dysfunction (dogs and cats): Intraurethral administration may assist manual bladder expression in patients with urine retention secondary to upper motor neuron lesions.
Dosage (Reference)
Dog
In dogs, atracurium is used extra-label as an adjunct to general anesthesia to provide controlled neuromuscular blockade. Mechanical ventilation and cardiovascular monitoring are mandatory during use.
| Clinical use | Route | Dose | Notes |
|---|---|---|---|
| Muscle relaxation during surgery or intubation | IV |
Initial: 0.1–0.25 mg/kg Maintenance: 0.1 mg/kg |
Do not repeat more frequently than every 20–30 minutes unless voluntary movement or nerve stimulation indicates recovery. Positive pressure ventilation is required. |
| Respiratory muscle paralysis during mechanical ventilation | IV |
Loading: 0.2–0.5 mg/kg CRI: 3–9 µg/kg/min |
Begin CRI 5 minutes after loading dose. Use 0.9% saline or 5% dextrose as diluent. Do not mix with other drugs. |
| Ophthalmic surgery (central bulbus positioning) | IV |
0.2 mg/kg once Then 0.1 mg/kg if needed |
Administer under general anesthesia. Repeat doses may be given during prolonged procedures. |
| Urinary retention (upper motor neuron lesion) | Intraurethral | 2–4 mL of 0.5 mg/mL solution |
Volume based on body weight. Catheter left in place for 5 minutes after instillation. |
• Requires mechanical ventilation and neuromuscular monitoring.
• Do not administer as a sole agent—general anesthesia must be established first.
• Intraurethral administration produces local effects with minimal systemic blockade.
Cat
In cats, atracurium is used extra-label to provide neuromuscular blockade during anesthesia and for specific intraurethral applications. Continuous monitoring and ventilatory support are essential.
| Clinical use | Route | Dose | Notes |
|---|---|---|---|
| Adjunctive muscle relaxation during anesthesia | IV |
Initial: 0.1–0.25 mg/kg Maintenance: 0.1 mg/kg |
Do not repeat more frequently than every 20–30 minutes unless recovery is evident. Positive pressure ventilation required. |
| Respiratory muscle paralysis during mechanical ventilation | IV |
Loading: 0.2–0.5 mg/kg CRI: 3–9 µg/kg/min |
Start CRI 5 minutes after loading dose. Use saline or dextrose solution only. |
| Removal of urethral plugs / urinary retention | Intraurethral | 2 mL of 0.5 mg/mL solution |
Instill slowly over 5 minutes with gentle urethral compression. Procedure may be repeated if obstruction persists. |
• Use only after induction of general anesthesia.
• Continuous respiratory and cardiovascular monitoring is mandatory.
• Intraurethral use is intended to provide local muscle relaxation.
Warnings & Precautions
Atracurium is a potent neuromuscular blocking agent that causes paralysis of skeletal muscles without providing sedation or analgesia. Its use in dogs and cats requires advanced anesthetic management, ventilatory support, and close monitoring to ensure patient safety.
- Not a sole agent: Atracurium must never be administered alone. It provides no analgesia or sedation and should only be given after general anesthesia has been induced.
- Ventilatory support required: Endotracheal intubation and positive-pressure ventilation are mandatory, as respiratory muscle paralysis will occur.
- Reversal agents availability: Anticholinesterase agents (e.g., neostigmine) and appropriate anticholinergics must be immediately available before administration.
- Monitoring requirements: Continuous monitoring of neuromuscular blockade, ventilation, cardiovascular status, and depth of anesthesia is essential to minimize overdose risk.
- Hypersensitivity: Contraindicated in dogs or cats with known hypersensitivity to atracurium. Use caution in patients with a history of reactions to other neuromuscular blocking agents due to possible cross-sensitivity.
- Conditions potentiating blockade: Use with extreme caution in patients with electrolyte abnormalities or neuromuscular disorders, as these conditions may enhance or prolong neuromuscular blockade.
- Histamine release: At higher-than-recommended doses, atracurium may cause histamine release. Use caution in dogs and cats where histamine-mediated effects could be hazardous.
- Ventilatory effects: Even partial neuromuscular blockade can reduce spontaneous ventilation and impair the response to hypercapnia.
- Recurarization risk: Residual drug in IV ports or fluid lines may lead to recurrent neuromuscular blockade after apparent recovery; thorough flushing of lines is recommended.
- Medication safety: Neuromuscular blocking agents must be stored separately from other medications with clear warning labels to prevent accidental administration.
Drug Interactions
Drug interactions with atracurium in dogs and cats primarily affect the degree or duration of neuromuscular blockade. When atracurium is used concurrently with the following agents, careful dose adjustment and close monitoring of neuromuscular function are required.
- Acetylcholinesterase inhibitors (e.g., neostigmine, pyridostigmine): Antagonize the neuromuscular blocking effects of atracurium and are used intentionally to reverse blockade at the end of anesthesia.
- Corticosteroids (e.g., dexamethasone, prednisolone): May enhance corticosteroid-associated neuromuscular weakness; consider therapy modification and monitor muscle strength.
- Other muscle relaxants and sedatives (e.g., alpha-2 agonists, benzodiazepines, methocarbamol): May produce synergistic or antagonistic effects on neuromuscular blockade.
- Phenobarbital: May decrease the intensity and duration of atracurium-induced neuromuscular blockade.
- Succinylcholine: May accelerate onset and enhance neuromuscular blockade; atracurium should not be administered until succinylcholine effects have resolved.
- Aminoglycoside antibiotics (e.g., amikacin, gentamicin): May enhance and prolong neuromuscular blockade.
- Inhalant anesthetics (e.g., isoflurane, sevoflurane): Can potentiate and prolong atracurium-induced neuromuscular blockade.
- Antiarrhythmic agents (e.g., procainamide, quinidine): May enhance neuromuscular blocking effects.
- Beta-adrenergic blockers: May increase the depth or duration of neuromuscular blockade.
- Calcium channel blockers: May potentiate neuromuscular blockade.
- Magnesium salts (parenteral): May significantly enhance neuromuscular blockade and prolong recovery.
- Tetracyclines and lincosamides: May increase neuromuscular blocking activity.
Side Effects & Overdose
Side Effects
Clinically significant adverse effects associated with atracurium are uncommon when recommended doses are used in dogs and cats. When they occur, adverse effects are most often related to histamine release or excessive neuromuscular blockade.
- Histamine-mediated reactions: Hypotension, vasodilation, tachycardia or bradycardia, bronchospasm, laryngospasm, dyspnea, rash, or urticaria may occur, particularly with rapid or high-dose administration.
- Prolonged neuromuscular blockade: Inadequate recovery or delayed return of muscle function may occur, especially with repeated dosing or continuous infusions.
- Injection site reactions: Transient irritation or local reactions may occur following IV administration.
- Central nervous system effects: The metabolite laudanosine is a CNS stimulant and has been associated with seizures; risk appears low but may increase with prolonged infusions.
- Respiratory effects: Partial neuromuscular blockade can reduce spontaneous ventilation and impair response to hypercapnia.
Overdose
Overdose of atracurium results in excessive and prolonged neuromuscular blockade, which can be life-threatening due to respiratory paralysis. Toxic dose thresholds have not been established for dogs or cats.
- Clinical signs: Profound muscle paralysis, prolonged apnea, hypotension, and signs of histamine release. Death may occur secondary to respiratory failure if ventilatory support is not provided.
- Immediate management: Secure the airway and provide controlled ventilation and cardiovascular support, including IV fluids and vasopressors as needed.
- Reversal of blockade: Neuromuscular blockade may be reversed using an anticholinesterase agent (e.g., neostigmine 0.02–0.04 mg/kg IV) administered with an appropriate anticholinergic. Reversal is typically evident within 8–10 minutes.
- Monitoring: Continued observation is essential, as the duration of atracurium action may exceed that of the reversal agent and repeat dosing may be required.
Key Notes
Practical clinical pearls specific to the use of atracurium in dogs and cats, highlighting points not emphasized in other sections:
- Depth of anesthesia: Neuromuscular blockade does not indicate adequate anesthetic depth; ensure sufficient anesthesia before and during atracurium administration.
- Predictable recovery: Because atracurium undergoes Hofmann elimination and ester hydrolysis, recovery is generally consistent and less dependent on organ function.
- Temperature sensitivity: Body temperature can influence drug elimination; hyperthermia may shorten duration of action, while hypothermia may prolong recovery.
- pH effects: Acid–base status can alter neuromuscular blockade, with acidosis potentially enhancing and prolonging effects.
- Neuromuscular monitoring: Objective monitoring techniques (e.g., peripheral nerve stimulation) improve dosing accuracy and reduce the risk of residual blockade.
- Urethral applications: Intraurethral use provides localized muscle relaxation with minimal systemic effects when performed correctly.
- Team communication: Clear communication among anesthesia and nursing staff is essential due to the paralytic nature of the drug.
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