The Need for a Long-Acting Local Anesthetic
Thought leaders have advocated that modern multi-modal analgesia regimens should incorporate local anesthetics due to their established efficacy.3,4 The local anesthetic class is the only class of analgesics that can completely block pain signals. In addition, local anesthetics are safe if administered at clinically recommended doses. Despite these efficacy and safety profiles, clinical use of local anesthetics as part of a multi-modal analgesic regimen remains uncommon.19 Explanations for the infrequent use include the technical difficulty associated with some nerve and epidural blocks; potential complications of an indwelling soaker catheter, and the short duration of action (< 8 hours) of the previously available local anesthetic solutions.
An Extended-Release Formula
In response to an unmet need for a long-acting local anesthetic, an extended-release formulation of bupivacaine was developed for use as a single-dose surgical site infiltration injection to provide post-operative analgesia in human patients, and received FDA-approval in October 2011. In August 2016, the Center for Veterinary Medicine (CVM) FDA-approved an extended-release formulation of bupivacaine to provide local post-operative analgesia for cranial cruciate ligament surgery in dogs. The extended-release bupivacaine technology used in this product consists of multivesicular liposomes composed of hundreds to thousands of chambers per particle, encapsulating aqueous bupivacaine.20 The liposomes are microscopic structures made of nonconcentric lipid bilayers that resemble a honeycomb matrix and are designed such that bupivacaine is gradually released from vesicles over a period of ≈ 96 hours (Figure 2).
The Technique for Instilling Bupivacaine Liposome Injectable Suspension into a Surgical Site
The technique for instilling bupivacaine liposome injectable suspension into a surgical site differs slightly from the use of a traditional bupivacaine formulation because the liposomes do not diffuse freely from where they are deposited as bupivacaine solution does. Therefore, a moving-needle tissue infiltration injection technique is used to inject the suspension into all tissue layers surrounding the surgical field (Figure 3). As bupivacaine is gradually released from individual liposomes, it will diffuse locally into the surrounding tissues. Bupivacaine liposome injectable suspension should not be coadministered with other local anesthetics, such as lidocaine, as these can cause premature release of bupivacaine from the liposomal vesicles.
Dosing and Administration Video
3. Epstein ME, Rodanm I, Griffenhagen G, et al. 2015 AAHA/AAFP pain management guidelines for dogs and cats. J Feline Med Surg. 2015;17(3):251-272.
4. Mathews K, Kronen PW, Lascelles D, et al. Guidelines for recognition, assessment and treatment of pain. J Small Ani. 2014;55(6):E10-E68.
19. Hunt JR, Knowles TG, Lascelles BD, Murrell JC. Prescription of perioperative analgesics by UK small animal veterinary surgeons in 2013. Vet Rec. 2015;176(19):493.
20. Spector MS, Zasadzinski JA, Sankaran MB. Topology of multivesicular liposomes, a model biliquid foam. Langmuir. 1996;12(20):4704-4708.