To the Editor:

With interest, we read the study by Li et al. [1], which evaluated the effect of prophylactic diphenhydramine on the catheter-related bladder discomfort (CRBD) after laparoscopic gynecologic surgery. We have some points to discuss based on their results.

First, they did not provide the effect size of their primary and secondary outcomes, which made it difficult to interpret the results and the compare it with the previous studies. P values alone cannot provide the magnitude of differences found [2].

Second, there was no significant effect at 1 h after surgery, although CRBD incidences at 2 and 6 h were significantly different. The authors attributed this to the poor assessment in drowsy patients. However, a previous network meta-analysis on this subject reported that many drugs significantly reduced the incidence of CRBD at 1 h after surgery including glycopyrrolate, ketamine, dexmedetomidine, oxybutynin, tolterodine, gabapentin as well as caudal block and dorsal penile nerve block [3]. Also, the incidence of moderate to severe CRBD does not seem to be different between the groups. These results suggest that the effect of diphenhydramine may be insufficient and other drugs could be superior to diphenhydramine in this setting.