Age‑stratified median effective dose (ED₅₀) of remimazolam besylate for successful gastroscope insertion without body movement in geriatric patients

BACKGROUND: Remimazolam besylate is increasingly used for procedure sedation anesthesia (PSA) in gastrointestinal endoscopy, but age‑specific dosing for elderly patients is unclear. This study determined the median effective dose (ED₅₀) for successful gastroscope insertion without patient movement in two geriatric age groups. METHODS: In a prospective single‑center trial, 51 patients were assigned by age to Group L (65-70 years, n = 27) or Group H (> 70 years, n = 24). All received 0.1 µg/kg sufentanil, followed by an initial remimazolam bolus of 0.15 mg/kg (Group L) or 0.10 mg/kg (Group H). Doses were adjusted in 0.02 mg/kg steps using a modified Dixon up‑and‑down method based on the previous patient's response (movement vs. no movement). Primary outcome was ED₅₀ for successful insertion. Secondary outcomes were the induction time, hemodynamic changes, hypoxemia, and other adverse events. RESULTS: was 0.171 mg/kg in Group L, significantly higher than 0.098 mg/kg in Group H (P < 0.001); probit analysis gave similar values (0.175 mg/kg vs. 0.106 mg/kg). ED₉₅ values were 0.235 mg/kg (Group L) and 0.131 mg/kg (Group H). Induction times were comparable (27 s vs. 25 s, P = 0.394). Both groups achieved rapid induction (< 1 min) and recovery time. Transient SpO₂ drops (< 95%) occurred in 1 patient (3.7%) in Group L and 2 patients (8.3%) in Group H; no hypoxemia (SpO₂ < 90%) was observed. Hypotension occurred in 7.4% (Group L) and 20.8% (Group H, P = 0.238). Movement incidence and VAS scores were similar. CONCLUSIONS: of remimazolam alone would be higher. This regimen provides rapid onset and recovery with low respiratory and circulatory risk in this cohort. However, the higher incidence of hypotension (20.8%) in patients > 70 years warrants increased vigilance for circulatory depression in this age group. TRIAL REGISTRATION: Chinese Clinical Trial Registry, No:ChiCTinR2500110081. Registered on 30 September 2025. Prospective registration. http://www.chictr.org.cn.