With the rapid increase in the ageing population, the use of procedural sedation and analgesia (PSA) for diagnostic procedures such as prostate biopsy in older adults is increasing. However, elderly patients are particularly susceptible to respiratory depression during PSA testing and have a significantly higher risk of hypoxaemia during procedures requiring deep sedation. Although propofol combined with fentanyl is commonly used, it frequently causes hypoxaemia and apnoea. Remimazolam, a novel ultrashort-acting benzodiazepine, may be a safer alternative with less respiratory compromise; however, the supporting evidence remains limited. This study aims to assess whether remimazolam combined with fentanyl reduces the incidence of respiratory depression compared with propofol combined with fentanyl in elderly patients undergoing prostate biopsy under deep sedation requiring immobility.

This is a single-centre, participant and assessor-blinded (with pragmatic blinding of participants), parallel-group, superiority randomised controlled trial conducted at the Jichi Medical University Saitama Medical Centre, Japan. Eligible participants are men aged ≥70 years who are scheduled to undergo prostate biopsy under intravenous sedation. Participants will be randomised in a 1:1 ratio to receive either remimazolam or propofol, each administered in combination with fentanyl at a fixed effect-site concentration. The primary outcome is the incidence of severe apnoea (≥1 min). The primary analysis will follow the intention-to-treat principle, implemented practically as a full analysis set analysed using a complete case approach. Sensitivity analyses will include a per-protocol analysis and multiple imputations of missing data. A subgroup analysis of patients aged ≥75 years was performed.

This study was approved by the Jichi Medical University Central Clinical Research Ethics Committee (approval number: 24JMU001S-2) and was registered with the Japan Registry of Clinical Trials on 11 November 2024. Written informed consent was obtained from all participants before enrolment. These findings will be disseminated through publications in peer-reviewed journals and presentations at scientific conferences.

jRCTs031240478.