A Phase I Study of the Pharmacokinetics, Pharmacodynamics, and Safety of Liposomal Bupivacaine for Sciatic Nerve Block in the Popliteal Fossa for Bunionectomy

This trial assessed the pharmacokinetics, pharmacodynamics, and safety of liposomal bupivacaine given via ultrasound-guided popliteal sciatic nerve block with or without immediate-release bupivacaine hydrochloride in adults having bunionectomies. 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 [C_max]), onset and duration of motor and sensory nerve block, and safety. Liposomal bupivacaine admixed with bupivacaine hydrochloride produced biphasic bupivacaine plasma disposition profiles with two distinct peaks. Geometric mean C_max of the early peak ranged from 235 to 421 ng/mL and the geometric mean of the late C_max was ∼30%-50% lower than the early peak. Median time to sensory block onset was 18 to 29 min in all cohorts. Sensory blocks lasted about twice as long with liposomal bupivacaine (median, 119-167 h) than with bupivacaine hydrochloride alone (median, 67 h). There were no serious adverse events. In conclusion, liposomal bupivacaine provided prolonged sensory nerve block when given as popliteal sciatic nerve blocks with or without bupivacaine hydrochloride, and bupivacaine plasma concentrations were well below the lower bound of the toxicity threshold of 2000 ng/mL for all cohorts.