Authors: Michele Carella et al.
Source: European Journal of Anaesthesiology 42(12):1043-1045, December 2025. DOI: 10.1097/EJA.0000000000002269
Summary
This editorial commentary by Carella et al. reviews a randomized controlled trial by Yousef et al. that rigorously re-examined a longstanding but poorly supported practice in regional anesthesia—the admixture of amide-type local anesthetics (LAs) such as lidocaine and ropivacaine. The authors explain that although clinicians often combine a “fast” agent with a “long-acting” one to speed onset while preserving duration, this approach is pharmacologically unsound and unsupported by recent data.
Yousef et al.’s trial compared three regimens for infraclavicular blocks: ropivacaine alone, a fixed-dose ropivacaine + lidocaine-epinephrine mix, and a reduced-dose ropivacaine + lidocaine-epinephrine mix. Contrary to traditional belief, the admixtures shortened block duration by several hours without improving sensory onset. This effect persisted even when the total ropivacaine dose was unchanged, indicating that admixture itself—through competitive sodium-channel binding or altered tissue kinetics—reduces block longevity.
The commentary explores the pharmacologic underpinnings of this finding: both lidocaine and ropivacaine act at the same sodium channel binding site, and concurrent administration leads to competition and potential interference with ion channel dynamics. Additionally, since both are metabolized hepatically via CYP1A2 and CYP3A4, co-administration introduces metabolic competition, particularly in patients with hepatic impairment or altered plasma protein binding.
Even the inclusion of epinephrine in the admixture, intended to limit systemic absorption, did not restore block duration to that achieved by ropivacaine alone. The authors emphasize that the results dismantle the old notion that mixing short- and long-acting amide anesthetics provides synergistic benefit. Instead, admixture introduces dilutional and pharmacodynamic disadvantages with potential toxicity implications.
Modern regional anesthesia, they argue, should rely on rational monotherapy at individualized doses—accounting for patient physiology and drug clearance—and consider adjuvants (such as intravenous dexamethasone) to enhance duration safely. The editorial concludes that precision, evidence, and pharmacologic integrity should replace outdated traditions of empiric mixing.
What You Should Know
• Mixing amide-type local anesthetics (e.g., lidocaine + ropivacaine) shortens block duration without improving onset.
• The interaction is not additive—these drugs compete for the same sodium-channel binding sites and metabolic pathways.
• Epinephrine modestly reduces systemic absorption but does not counteract the loss in duration.
• Rational monotherapy, ideally combined with evidence-based adjuvants such as intravenous dexamethasone, offers superior safety and predictability.
• Abandoning non-evidence-based admixture practices aligns with the modern goals of regional anesthesia: precision, safety, and pharmacologic consistency.
Thank you to the European Journal of Anaesthesiology for allowing us to use this article.