Pharmacologic adjuvants in peribulbar anesthesia: a narrative review with a comparative and decision-oriented framework

Peribulbar anesthesia is widely used in ophthalmic surgery because it offers a favorable balance between efficacy and safety. However, clinically meaningful variability in block onset, duration, and akinesia quality persists despite technical advances. Pharmacologic adjuvants are commonly added to improve block performance; however, much of the available evidence is extrapolated from peripheral nerve block literature and does not fully account for the unique anatomic and physiologic characteristics of the peribulbar space. This narrative review critically synthesizes current evidence on commonly used pharmacologic adjuvants in peribulbar anesthesia, including dexmedetomidine, magnesium sulfate, fentanyl, and rocuronium, using a peribulbar-specific framework. Evidence is interpreted across key clinical domains relevant to ophthalmic anesthesia practice, including block onset, reliability of akinesia, duration of analgesia, ocular physiology, sedation, hemodynamic stability, and injectate volume considerations. Available data indicate that these adjuvants exert distinct and non-interchangeable effects. Dexmedetomidine provides the most consistent prolongation of block duration and improves reliability with cooperative sedation. Magnesium sulfate offers a hemodynamically stable option with favorable effects on intraocular pressure without sedation. Fentanyl and rocuronium primarily enhance onset and early surgical readiness, with limited impact on block duration. Injectate volume emerges as a critical determinant of ocular safety within the confined orbital space, and pharmacologic adjuvants may improve block quality without necessitating potentially risky increases in volume. Rather than identifying a universally optimal agent, this review supports a goal-directed, peribulbar-specific approach to adjuvant selection that integrates procedural priorities, patient characteristics, ocular safety, and volume constraints to guide individualized, evidence-informed clinical practice.