BACKGROUND AND OBJECTIVES:The objective of this study was to assess the pharmacokinetics, sensory/motor effects, and safety of epidurally administered liposome bupivacaine versus bupivacaine HCl in healthy volunteers. METHODS:Thirty subjects were randomized to receive liposome bupivacaine 89, 155, or 266 mg, or bupivacaine HCl 50 mg in a double-blind fashion. Occurrence/duration of motor blockade, pinprick/cold sensitivity, and plasma bupivacaine levels were assessed for 96 hours after study drug administration. Tolerability parameters were also assessed. RESULTS:All doses of liposome bupivacaine resulted in greater area under the curve and a longer time to observed maximum plasma concentration and terminal elimination half-life than bupivacaine HCl 50 mg. Mean maximum plasma concentration with liposome bupivacaine 89 and 155 mg (but not 266 mg) was statistically significantly lower than with bupivacaine HCl 50 mg (P < 0.001). Median duration of motor blockade with liposome bupivacaine 266 mg was 1 hour versus 2.8 hours for bupivacaine HCl. Of subjects who received liposome bupivacaine 266 mg, 29% (2/7) were unable to ambulate at 4 hours postdose versus 67% (4/6) of those receiving bupivacaine HCl. Median durations of pinprick/cold sensitivity loss were 36 and 69 hours, respectively, in the liposome bupivacaine 266-mg group versus 12 hours for both pinprick and cold in the bupivacaine HCl group. Liposome bupivacaine was well tolerated; the most common adverse event in all treatment groups was injection site pain, which resolved within 30 days for most subjects. CONCLUSIONS:Epidurally administered liposome bupivacaine 266 mg resulted in a longer duration of sensory blockade than liposome bupivacaine 89 or 155 mg or bupivacaine HCl 50 mg. Duration of motor blockade was shorter with liposome bupivacaine 266 mg versus bupivacaine HCl.