Understanding Atracurium and Its Role
Atracurium besylate is a non-depolarizing neuromuscular blocking agent used to provide skeletal muscle relaxation during surgery or mechanical ventilation [1.2.4, 1.3.5]. It is administered intravenously by a trained medical professional to facilitate endotracheal intubation and optimize surgical conditions [1.9.3, 1.3.3]. Unlike other agents, its metabolism is largely independent of liver or kidney function, occurring through a process called Hofmann elimination in the plasma [1.3.1]. This unique characteristic makes it a valuable option in certain clinical scenarios [1.3.2]. However, like all medications, it is associated with a range of potential side effects.
The Mechanism Behind the Effects
Atracurium works by competitively blocking acetylcholine receptors at the neuromuscular junction's motor end-plate [1.3.3]. This action prevents muscle cells from depolarizing, leading to muscle relaxation and paralysis. While this is the intended therapeutic effect, atracurium can also trigger the release of histamine, a natural compound involved in local immune responses. Many of the drug's most common side effects are directly linked to this dose-dependent histamine release [1.2.4, 1.5.4].
Common and Mild Side Effects
The most frequently observed adverse reactions to atracurium are generally mild and transient, often related to histamine release [1.2.5]. These include:
- Cutaneous Reactions: The most common side effect is skin flushing, particularly of the face and arms [1.2.2, 1.2.4]. Other skin reactions can include redness (erythema), itching (pruritus), hives (urticaria), and rashes [1.2.2, 1.4.4].
- Injection Site Reactions: Pain or irritation may occur at the injection site [1.2.1].
- Cardiovascular Changes: Mild and temporary changes in blood pressure and heart rate can occur. Some patients may experience a slight drop in blood pressure (hypotension) or a reflex increase in heart rate (tachycardia) [1.2.3, 1.5.1].
These effects are often of little clinical significance unless they are associated with more substantial hemodynamic changes [1.2.3].
Serious and Less Common Side Effects
While less frequent, atracurium can cause more severe adverse reactions that require immediate medical attention. These are more likely at higher doses or in susceptible individuals [1.5.4].
Cardiovascular and Respiratory Complications
- Significant Hypotension: In some patients, especially those with pre-existing cardiovascular disease, the drop in blood pressure can be significant, leading to dizziness, blurry vision, or feeling faint [1.2.1, 1.5.4]. Overdose can particularly increase this risk [1.5.3].
- Bronchospasm and Respiratory Issues: The histamine release can cause wheezing, increased bronchial secretions, shortness of breath (dyspnea), and in some cases, constriction of the airways (bronchospasm) or voice box (laryngospasm) [1.2.2, 1.5.1]. This is a particular concern for patients with a history of asthma [1.9.1].
- Bradycardia: Unlike some other muscle relaxants, atracurium does not counteract the slowing of the heart rate (bradycardia) that can be caused by some anesthetic agents or vagal stimulation. As a result, bradycardia may be more common with atracurium [1.9.3, 1.3.1].
- Anaphylaxis: Severe, life-threatening allergic reactions (anaphylaxis) have been reported, although they are rare [1.2.3, 1.6.3]. These reactions can be fatal and require immediate emergency treatment [1.9.4].
Neuromuscular and Other Systemic Effects
- Prolonged Blockade: In some cases, the muscle paralysis can last longer than expected (prolonged block) or be insufficient for the procedure (inadequate block) [1.2.3]. Patients with neuromuscular diseases like myasthenia gravis are especially sensitive to these effects [1.9.1].
- Seizures: A metabolite of atracurium, laudanosine, can cross the blood-brain barrier and is known to be a central nervous system stimulant with the potential to cause seizures at high concentrations [1.6.1, 1.6.4]. While rare spontaneous reports of seizures exist for ICU patients on long-term atracurium infusions, clinical studies have generally found that the laudanosine levels produced by standard clinical doses are unlikely to cause this effect [1.6.3, 1.6.4, 1.9.1]. The risk may be higher in patients with pre-existing conditions like head trauma or uremia [1.9.1].
- Malignant Hyperthermia: Although extremely rare with atracurium, it is a known, potentially fatal complication associated with general anesthesia. Clinicians must be prepared for this possibility [1.9.3, 1.4.5].
Comparison with Other Neuromuscular Blockers
Atracurium's side effect profile differs from other common neuromuscular blockers like cisatracurium and rocuronium.
| Feature | Atracurium | Cisatracurium | Rocuronium |
|---|---|---|---|
| Histamine Release | Significant potential, dose-dependent [1.5.4] | Minimal to no histamine release [1.7.2] | Minimal histamine release [1.6.5] |
| Cardiovascular Effects | Can cause hypotension and reflex tachycardia due to histamine release [1.2.3] | Excellent cardiovascular stability, minimal changes to heart rate or blood pressure [1.7.2] | Primarily causes mild to moderate tachycardia; generally stable hemodynamics [1.10.4] |
| Metabolite Concerns | Produces laudanosine, with a theoretical seizure risk [1.6.1] | Also produces laudanosine, but in smaller amounts due to higher potency [1.6.4, 1.6.5] | No active metabolites of concern [1.7.2] |
| Anaphylaxis Risk | Lower reported incidence than rocuronium [1.10.3, 1.10.4] | Considered to have a very low risk of anaphylaxis [1.10.3] | Higher reported incidence of anaphylaxis compared to other NMBAs [1.10.3, 1.10.4] |
Cisatracurium, an isomer of atracurium, is often preferred as it is more potent, produces less laudanosine, and has significantly less histamine-releasing potential, leading to greater hemodynamic stability [1.7.2, 1.7.4].
Management and Conclusion
Management of atracurium's side effects involves careful patient monitoring and prompt intervention. For hypotension related to histamine release, treatment may include fluid administration and vasopressor agents [1.8.1]. The neuromuscular blockade itself can be reversed with acetylcholinesterase inhibitors like neostigmine, typically administered with atropine or glycopyrrolate to manage muscarinic side effects [1.8.1, 1.8.4].
In conclusion, while atracurium is an effective and widely used medication, it carries a distinct profile of side effects primarily driven by histamine release. The most common effects are cutaneous reactions and mild hypotension. More severe complications, such as bronchospasm and anaphylaxis, are less common but require vigilance, especially in high-risk patients. The potential for laudanosine-induced CNS stimulation exists but is rarely a clinical issue with standard dosing. Understanding these potential adverse events allows clinicians to use atracurium safely and manage its effects effectively. An authoritative resource for further information is the StatPearls article on Atracurium from the NIH.
