Journal Scan: How effective are buprenorphine’s analgesic effects in cats?
Why they did it
Despite widespread use in the clinical setting, buprenorphine has been shown to provide variable analgesia, and patient response may be inconsistent. The authors provide an overview of the available literature pertaining to analgesic effects of buprenorphine in cats.
What they did
The authors conducted a review of the literature published between 1970 and 2013 regarding the use of buprenorphine in cats. Twenty-two original research studies, 14 clinical studies, one retrospective study, and two case series were reviewed.
What they found
Buprenorphine is a partial mu agonist, though the authors note that its pharmacologic profile is complex. Several studies found that the route of buprenorphine administration has a significant effect on antinociception and analgesia. For example, while previous studies have indicated that buccal administration results in high bioavailability, the authors note that this may have been disproven by other studies when samples were collected from the carotid vs. the jugular veins for comparison.
Two studies also demonstrated that clinical response was inadequate for cats treated with buccal buprenorphine following ovariohysterectomy. Studies evaluating the effect of transdermal buprenorphine on pain scores in cats following ovariohysterectomy found that, despite achieving high plasma concentrations, this route provides suboptimal analgesia. Adverse effects such as vomiting, nausea, or dysphoria are rare, but mild increases in body temperature have been reported. Mydriasis and behavioral changes such as purring, kneading, and rolling are common and do not correlate with analgesia or antinociception.
The authors note that a subcutaneous sustained release buprenorphine formulation is available, but there are no studies evaluating its use in cats at this time.
Administration of buprenorphine in conjunction with other opioids has also been evaluated. Coadministration with butorphanol did not provide better antinociception than either drug alone, according to one study.
Routine pain assessment will be integral to successful use of buprenorphine in the clinical setting. Buprenorphine has a delayed onset of action, and analgesic effects may take 30 to 45 minutes following intravenous or intramuscular injection. The authors also point out that duration of action may be shorter than previously thought and repeated dosing may be required. For this reason, cats should be consistently re-evaluated for pain following buprenorphine administration. Whenever possible, intravenous is the preferred route of administration (0.02 mg/kg), as it will have the fastest speed of onset and superior duration of action compared with other routes. Buccal buprenorphine should be reserved for cats that have received premedication with a full mu agonist such as morphine, methadone, or fentanyl. A multimodal analgesic plan that includes a nonsteroidal anti-inflammatory agent or loco-regional anesthesia should be considered whenever possible.
Steagall PVM, Monteiro-Steagall BP, Taylor PM. A review of the studies using buprenorphine in cats. J Vet Intern Med 2014;28:762-770.
Link to full article: http://onlinelibrary.wiley.com/doi/10.1111/jvim.12346/full.