What question did this study set out to answer?

This research aimed to evaluate how quickly three different formulations of extended-release buprenorphine induce analgesia in rats.

April 22, 2026

Onset of Analgesia in Rats (Rattus norvegicus) for Three Buprenorphine Formulations

Key Points

This research aimed to evaluate how quickly three different formulations of extended-release buprenorphine induce analgesia in rats.
Forty Sprague-Dawley rats were assigned to four treatment groups: saline, Bup-ER, Ethiqa-XR, and LAT-Bup.
Analgesic effectiveness was determined using a hot plate test at multiple time points after drug administration.
Plasma levels of buprenorphine were measured to compare therapeutic thresholds.
Bup-ER showed a significant increase in thermal latency starting at 45 minutes after administration.
Ethiqa-XR reached significant thermal latency at 180 and 240 minutes.
LAT-Bup increased in thermal latency at 120, 180, and 240 minutes.

Abstract

Extended-release buprenorphine has been extensively used in laboratory animal medicine, yet its onset of analgesia in rats remains largely unexplored. This study aimed to investigate the analgesic onset of 3 different extended-release buprenorphine formulations in rats. Our hypothesis was that the onset of all 3 buprenorphine formulations are comparable and are detectable as early as 5 minutes after administration in rats. Sprague-Dawley rats (both male and female, n = 40) were randomly assigned to 4 treatment groups: (1) saline (1 mL/0.1 kg SC, once); (2) Bup-ER (1.2 mg/kg SC, once); (3) Ethiqa-XR (0.65 mg/kg SC, once); and (4) LAT-Bup (Zorbium, 10 mg/kg transdermal, once). Thermal sensitivity (using a hot plate test) was assessed at time points of 5, 15, 30, 45, 60, 120, 180, and 240 minutes following drug administration. Results were as follows: (1) compared with the saline group, Bup-ER's thermal latency significantly increased at 45 (11.05 ± 1.13), 60 (12.5 ± 1.16), 120 (13.7 ± 1.24), 180 (12.48 ± 0.81), and 240 (11.64 ± 0.7) minutes; (2) Ethiqa-XR's thermal latency significantly increased at 180 (12.01 ± 0.6) and 240 (11.76 ± 0.81) minutes; and (3) LAT-Bup's thermal latency significantly increased at 120 (11.27 ± 1.16), 180 (13.97 ± 1.35), and 240 (14.8 ± 1.26) minutes. There were no differences between sexes. LAT-Bup and Bup-ER provided buprenorphine plasma levels exceeding the purported therapeutic threshold of 1 ng/mL by 5 minutes, while Ethiqa-XR exceeded the threshold at 45 minutes. We concluded that these 3 buprenorphine extended-release formulations did not exhibit a time to onset of analgesia within 5 minutes. This study demonstrates that despite all 3 extended-release formulations reaching a purported plasma therapeutic threshold earlier, the clinical onset of analgesia for the hot plate test was shortest for Bup-ER (45 minutes), followed by LAT-Bup (120 minutes) and Ethiqa-XR (180 minutes) in Sprague-Dawley rats.

اسأل الذكاء الاصطناعي

Bookmark