Antinociceptive Effect of Liposomal Bupivacaine Formulations After Intrathecal Administration in Rats

Area of Science:

• Pharmacology
• Neuroscience
• Drug Delivery Systems

Background:

• Previous in vitro studies indicated potential benefits of multilamellar liposomal bupivacaine (MLB) over bupivacaine alone.
• Research aimed to validate these findings in vivo for antinociceptive effects.

Purpose of the Study:

• To investigate the in vivo antinociceptive effect of intrathecal MLB.
• To compare the efficacy and duration of antinociception and motor block of MLB and high-yield drug entrapment in liposome (HYDEL) bupivacaine against control bupivacaine.

Main Methods:

• Prepared MLB and HYDEL bupivacaine formulations.
• Administered drugs intrathecally to 18 Wistar rats divided into control (bupivacaine), MLB, and HYDEL bupivacaine groups.
• Assessed antinociception via tail flick latency (TFL) test and documented motor block.

Main Results:

• Intrathecal HYDEL bupivacaine produced significantly longer TFL times compared to control and MLB groups (P < 0.05).
• Maximum possible effect (MPE) of 100% was observed with HYDEL bupivacaine between 10-45 min; control and MLB groups showed MPEs of 70% and 50%, respectively.
• Motor block duration was shorter in HYDEL and MLB groups (20 min) compared to the control group (75 min).

Conclusions:

• Intrathecal administration of MLB and HYDEL bupivacaine in rats demonstrated enhanced antinociceptive activity.
• These liposomal formulations resulted in a longer duration of pain relief with a reduced duration of motor blockade.