Atracurium

BRAND NAMES

Tracrium – the primary brand name widely used internationally. 

Tracurium – a variant used in some regions.

MECHANISM OF ACTION

Atracurium is a non-depolarizing neuromuscular-blocking agent that induces skeletal muscle relaxation by competitively inhibiting acetylcholine at nicotinic receptors in the neuromuscular junction. By preventing acetylcholine from binding, it blocks depolarization of the muscle membrane, resulting in muscle paralysis without initial contraction. This makes it useful for facilitating tracheal intubation and providing muscle relaxation during surgery or mechanical ventilation. Atracurium is unique among neuromuscular blockers because it is metabolized through Hofmann elimination and ester hydrolysis, allowing safe use in patients with renal or hepatic impairment.

PHARMACOKINETICS

Absorption

Atracurium is not absorbed orally and must be administered intravenously for clinical use. After IV administration, it rapidly distributes into the plasma and reaches effective concentrations at the neuromuscular junction within 2 to 5 minutes, allowing prompt onset of muscle relaxation.

Distribution

After intravenous administration, atracurium is rapidly distributed throughout the extracellular fluid, including skeletal muscles. It has a relatively small volume of distribution, approximately 0.2–0.3 L/kg, and is largely confined to plasma and extracellular compartments. Atracurium is about 80% bound to plasma proteins, which influences its duration of action and helps limit accumulation in tissues.

Metabolism

Atracurium is primarily broken down in the body through Hofmann elimination, a non-enzymatic process that occurs at physiological pH and temperature, producing inactive metabolites. These pathways make atracurium independent of liver and kidney function, allowing safe use in patients with hepatic or renal impairment.

Elimination

Atracurium is eliminated primarily through its metabolism rather than renal or hepatic excretion. The majority of the drug is broken down by Hofmann elimination and ester hydrolysis into inactive metabolites, which are then excreted in the urine and bile. Only a small fraction of unchanged atracurium is excreted by the kidneys, making it suitable for patients with impaired liver or kidney function.

PHARMACODYNAMICS

Atracurium is a non-depolarizing neuromuscular-blocking agent that produces skeletal muscle relaxation by competitively inhibiting acetylcholine at nicotinic receptors in the neuromuscular junction. The onset of action is typically 2 to 5 minutes after intravenous administration, and its effects last about 20 to 40 minutes, depending on the dose. Atracurium’s muscle relaxant effect is dose-dependent, and recovery occurs gradually as the drug is metabolized by Hofmann elimination and ester hydrolysis. Histamine release may occur at higher doses, occasionally causing mild hypotension or flushing.

ADMINISTRATION

Atracurium is given intravenously as a bolus or infusion to induce and maintain skeletal muscle relaxation during surgery or mechanical ventilation. Doses are adjusted by weight and clinical condition, with neuromuscular monitoring recommended.

DOSAGE AND STRENGTH

Atracurium is typically available as a solution for intravenous injection at a concentration of 10 mg/mL. For adults, the usual intubating dose is 0.4 to 0.5 mg/kg, providing muscle relaxation within 2 to 3 minutes. Maintenance doses of 0.1 to 0.2 mg/kg may be given as needed to prolong the neuromuscular blockade, or a continuous infusion of 5 to 10 mcg/kg/min can be used during longer procedures. Pediatric doses are adjusted according to weight and age, and careful monitoring of neuromuscular function is recommended to prevent prolonged paralysis.

DRUG INTERACTIONS

Atracurium’s effects can be increased by antibiotics, inhalational anesthetics, magnesium, and calcium channel blockers, and may be reduced by drugs that increase acetylcholine. Neuromuscular monitoring is recommended when used with these agents.

FOOD INTERACTIONS

Atracurium does not have any known significant interactions with food. Its administration is exclusively intravenous, so oral intake or dietary habits do not affect its absorption, distribution, or efficacy.

CONTRAINDICATIONS

Atracurium is contraindicated in patients with known hypersensitivity to atracurium or other benzylisoquinolinium compounds. Caution is required in patients with severe hypotension or hemodynamic instability, as histamine release can worsen these conditions. It should also be used carefully in patients with myasthenia gravis or other neuromuscular disorders, as they may have increased sensitivity to non-depolarizing neuromuscular blockers.

SIDE EFFECTS

• Hypotension (due to histamine release) 

• Flushing of the skin 

• Bronchospasm or mild respiratory effects 

• Tachycardia or transient changes in heart rate 

• Rare allergic reactions or anaphylaxis 

• Prolonged neuromuscular blockade in sensitive individuals 

• Rare seizures or myopathy in patients with predisposing conditions

TOXICITY

Atracurium has a relatively low systemic toxicity when used at recommended doses. Overdose can lead to prolonged neuromuscular blockade, resulting in respiratory depression or apnea, which requires mechanical ventilation until recovery. Excessive doses may also increase the risk of histamine-mediated reactions, such as hypotension, flushing, or rarely, bronchospasm. Atracurium is not known to cause significant organ toxicity, as it is metabolized via Hofmann elimination and ester hydrolysis independent of liver or kidney function.