Does Atracurium Cause Pupil Dilation?
No, atracurium does not cause pupil dilation (mydriasis). Atracurium is a neuromuscular blocking agent that acts exclusively at the motor end plate of skeletal muscles and has no direct effect on the autonomic nervous system or pupillary function 1, 2.
Mechanism of Action and Pupillary Effects
Atracurium is a benzylisoquinolinium non-depolarizing neuromuscular blocking agent that competitively binds to cholinergic receptors at the motor end plate without affecting autonomic ganglia or pupillary muscles 2, 3.
The drug does not cross the blood-brain barrier and has no central nervous system effects that would influence pupillary size 1.
Unlike some other neuromuscular blocking agents (such as pancuronium which has vagolytic effects), atracurium has minimal cardiovascular or autonomic effects at standard doses 1.
Important Clinical Caveat: Histamine Release
Atracurium can cause histamine release, particularly with rapid administration or high doses, but this produces hypotension and flushing—not pupillary changes 1.
Histamine release is a direct mast cell effect rather than an autonomic phenomenon and does not affect pupillary diameter 1.
Cisatracurium, an isomer of atracurium, releases virtually no histamine and is preferred for prolonged use 1, 3.
Common Causes of Mydriasis During Anesthesia
If pupil dilation occurs during anesthesia when atracurium has been administered, consider these actual causes:
Anticholinergic drugs: Atropine or glycopyrrolate given for reversal of neuromuscular blockade can cause mydriasis, especially in large doses 4, 5.
Topical agents: Inadvertent contamination with phenylephrine or other mydriatic drops used for airway preparation 6, 7.
Neurological injury: Acute intracranial pathology, impaired venous return, or direct trauma 6.
Pre-existing conditions: Unrecognized baseline pupillary abnormalities 6.
Clinical Bottom Line
If mydriasis occurs in a patient receiving atracurium, investigate other causes including co-administered anticholinergics, topical agents, or neurological complications 6, 4.
The neuromuscular blocking properties of atracurium are confined to skeletal muscle and do not extend to smooth muscle of the iris 1, 3.