The results of this study demonstrated that administration of 2 mg sublingual buprenorphine effectively reduced pain in patients with acute renal colic. Although the number of patients was not enough to perform equivalency tests, the results showed that the analgesic effect of buprenorphine was comparable to 0.1 mg/kg IV morphine.
To the best of our knowledge, there are no other studies on sublingual buprenorphine in the treatment of renal colic in the ED. However, our results are compatible with the results of a previous study in this center on the effectiveness of sublingual buprenorphine in acute bone fractures [
6]. In that study, patients with acute extremity fractures received either sublingual buprenorphine (0.4 mg) or IV morphine (5 mg). The pain scores were compared after 30 and 60 minutes and there was no significant difference between the two groups [
6]. Our results are also comparable with the results of Risbo et al. [
9] and Abid et al. [
10], who studied buprenorphine in post-operative pain management. In the first study, buprenorphine was compared with intramuscular morphine as an analgesic for pain management after elective knee joint surgery, where they demonstrated similar efficacy [
9]. In the second study, Abid et al. found buprenorphine as effective as morphine for post-operative pain management in patients undergoing a Caesarean section [
10]. Furthermore, according to the findings of this study, patients in the buprenorphine group reported dizziness more frequently but other adverse effects observed within 40 minutes were similar in the two groups. Walsh et al. [
11] showed that increasing buprenorphine dose will increase its analgesic effect but not its side effects. Comparing to the results of a study in which lower dose of buprenorphine was used (0.4 mg) and no adverse effect was reported [
6], it seems that higher doses will increase analgesic efficacy without affecting the side effects.
Limitations
Our study faced several limitations. First, many patients had to be excluded due to previous use of opioids or addiction. Secondly, some of the patients might have been drug seekers and IV drug users imitating renal colic to get morphine. It is possible that they were not recognized and were included in study. Thirdly, NRS may be an inappropriate measurement upon arrival of the patients as they tend to choose the highest NRS (i.e., 10), assuming that this will accelerate their treatment process. It may justify the number of patients whose NRS was 10 at the beginning; however, this situation is expected to be similar in both groups and does not seem to influence the change in NRS during the observation time. Another limitation of our study was the use of 2 mg buprenorphine tablets which may be the cause of slightly higher rate of side effects in this group; using smaller doses and then titrating it to effect may reduce the occurrence of side effects. Finally, this study did not find a significant difference between the two groups probably because of the small sample size.