Study questions liposomal bupivacaine’s value in bearded dragons
Bottom line
A new American Journal of Veterinary Research study suggests liposomal bupivacaine may not deliver the longer neuraxial block many clinicians would expect in inland bearded dragons. In a randomized, blinded, crossover trial, investigators Tatiana Henriques Ferreira, Johnny A. Uelmen, and Dustin M. Fink compared neuraxial liposomal bupivacaine with standard bupivacaine hydrochloride in 12 adult bearded dragons and found that the liposomal formulation did not prolong blockade and produced less consistent motor blockade than conventional bupivacaine. The work builds on earlier bearded dragon neuraxial anesthesia research from the same group, which had already shown standard bupivacaine can produce relatively short-lived pelvic limb and cloacal blockade in this species. (avmajournals.avma.org)
Why it matters: For veterinary professionals managing reptile anesthesia and analgesia, the finding is a reminder that extended-release local anesthetic formulations don’t necessarily translate across species, routes, or tissues. Liposomal bupivacaine is designed as a multivesicular, slow-release formulation, but its labeled human uses are infiltration and selected perineural nerve blocks, not neuraxial administration, and product labeling warns that formulation characteristics can affect performance. In other veterinary species, liposomal bupivacaine has shown mixed results, including prolonged block in some canine peripheral nerve studies and variable duration in horses, so the bearded dragon result adds species- and route-specific caution. (dailymed.nlm.nih.gov)
What to watch: Watch for follow-up reptile analgesia studies testing whether other neuraxial drug combinations, doses, or adjuvants offer more reliable duration without sacrificing motor consistency. (avmajournals.avma.org)
Key facts
- Study type
- Randomized, blinded, crossover trial
- Species
- 12 adult inland bearded dragons (Pogona vitticeps)
- Comparison
- Liposomal bupivacaine vs. standard bupivacaine hydrochloride
- Route
- Neuraxial injection
- Dose
- Bupivacaine hydrochloride 1.5 mg/kg; liposomal bupivacaine 4 mg/kg
- Washout
- 7 days
- Main finding
- Liposomal bupivacaine did not prolong blockade
- Motor effect
- Less consistent motor blockade than conventional bupivacaine
- Sedation
- Alfaxalone
Liposomal bupivacaine didn’t outperform standard bupivacaine hydrochloride for neuraxial blockade in inland bearded dragons, according to a new study in the American Journal of Veterinary Research. Instead of extending blockade, the liposomal formulation produced less consistent motor effects, undercutting the assumption that a slow-release product will automatically provide longer regional anesthesia in exotic species.
That matters because neuraxial anesthesia has become an important option for procedures involving the tail, cloaca, and caudal coelom in bearded dragons. Earlier AJVR work from this research group and collaborators helped establish the technique in this species, showing that neuraxial local anesthetics can create pelvic limb, cloacal, and midcaudal trunk blockade with rapid onset but relatively limited duration. In a 2022 study, the same line of research reported that standard neuraxial bupivacaine in bearded dragons produced pelvic limb motor blockade with a median duration of about 68 minutes, highlighting the clinical appeal of any strategy that might safely extend effect. (avmajournals.avma.org)
The new study, by Tatiana Henriques Ferreira, Johnny A. Uelmen, and Dustin M. Fink, used a randomized, crossover, blinded design in 12 adult bearded dragons sedated with alfaxalone. According to the abstract provided by AJVR, each animal received both treatments with a 7-day washout: standard bupivacaine hydrochloride at 1.5 mg/kg and liposomal bupivacaine at 4 mg/kg, each administered neuraxially at 0.3 mL/kg. The headline finding was straightforward: liposomal bupivacaine did not prolong neuraxial blockade and produced less consistent motor blockade than the conventional formulation.
The result is notable because liposomal bupivacaine has a strong theoretical appeal. The formulation is a multivesicular liposomal suspension designed to release bupivacaine over time. In human medicine, the branded product EXPAREL is labeled for local infiltration and certain perineural nerve blocks, including interscalene brachial plexus, sciatic popliteal, and adductor canal blocks, rather than neuraxial use. The label also notes that the product’s physicochemical properties can be altered by admixture or local exposure to some other anesthetics, underscoring that performance depends heavily on route and handling. (dailymed.nlm.nih.gov)
Veterinary experience with liposomal bupivacaine has also been uneven across indications. In dogs, one AJVR study found substantially longer blockade after ultrasound-guided sciatic nerve block with a liposomal suspension, although motor and proprioceptive deficits were inconsistent over time. In horses, another AJVR study reported high variability in duration after perineural administration, even when analgesic effects were present. Taken together, those data suggest the bearded dragon findings are less an outlier than another example that this formulation’s real-world effect is highly context dependent. (avmajournals.avma.org)
Why it matters: For veterinarians working with reptiles and other exotic species, this study is a practical caution against assuming that a premium, extended-release formulation will improve neuraxial anesthesia simply because it can prolong effect in some peripheral applications. Route matters, tissue environment matters, and species physiology matters. If liposomal bupivacaine yields less predictable motor blockade without extending duration, its value proposition becomes much weaker for procedures where reliable onset, spread, and recovery are essential. That’s especially relevant in reptile patients, where anesthetic monitoring and recovery can already be less forgiving than in dogs and cats.
There’s also a stewardship angle for specialty and referral practices. Liposomal bupivacaine products carry handling constraints and are not broadly labeled for neuraxial use in humans, while veterinary evidence remains mixed by species and block type. For clinicians, that means protocol decisions should stay grounded in species-specific data rather than extrapolation from canine, equine, or human literature. (dailymed.nlm.nih.gov)
What to watch: The next step is likely more refinement than replacement, including work on alternative neuraxial combinations, dose optimization, and adjunctive analgesics in reptiles. Prior AJVR work showed neuraxial morphine combined with lidocaine produced regional antinociception in bearded dragons for at least 12 hours, which may keep multimodal neuraxial strategies in focus as clinicians look for longer-lasting, clinically reliable reptile analgesia. (avmajournals.avma.org)