November 29, 2025
Background: This trial assessed the pharmacokinetics, pharmacodynamics, and safety of liposomal bupivacaine administered via ultrasound-guided popliteal sciatic nerve block with or without immediate-release bupivacaine hydrochloride in adults undergoing bunionectomy.
Methods: Forty-five adults were enrolled into four sequential cohorts: (1) liposomal bupivacaine 266 mg with bupivacaine hydrochloride 50 mg; (2) liposomal bupivacaine 133 mg with bupivacaine hydrochloride 50 mg; (3) liposomal bupivacaine 266 mg; or (4) bupivacaine hydrochloride 100 mg. Outcomes included pharmacokinetics (e.g., bupivacaine maximum plasma concentration [Cmax]), onset and duration of motor and sensory nerve block, and safety.
Results: Liposomal bupivacaine admixed with bupivacaine hydrochloride produced biphasic bupivacaine plasma disposition profiles with two distinct peaks. The geometric mean Cmax of the early peak ranged from 235 to 421 ng/mL, and the geometric mean of the late Cmax was approximately 30%-50% lower than the early peak. Median time to sensory block onset was 18 to 29 minutes in all cohorts. Sensory blocks lasted about twice as long with liposomal bupivacaine (median, 119-167 hours) than with bupivacaine hydrochloride alone (median, 67 hours). There were no serious adverse events. Bupivacaine plasma concentrations remained well below the lower bound of the toxicity threshold of 2000 ng/mL in all cohorts.
Conclusions: Liposomal bupivacaine provided prolonged sensory nerve block when administered as a popliteal sciatic nerve block with or without bupivacaine hydrochloride and maintained plasma bupivacaine concentrations below the toxicity threshold.
Keywords: anesthesia; foot and ankle surgery; immediate-release bupivacaine; liposomes; postoperative pain; ultrasound-guided nerve block.
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