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Purpose: Intrathecal dexmedetomidine (DEX) has been used to improve the quality and duration of spinal anesthesia. The aim of this meta-analysis is to evaluate whether intrathecal DEX could prolong the duration of sensory and motor block during spinal anesthesia., Methods: We searched PubMed, EMBASE, Web of Science, and the Cochrane Library for randomized controlled trials that investigated the facilitatory effects of intrathecal administration of DEX compared with those of a placebo on spinal anesthesia from inception to April 2019. Sensory and motor block durations, sensory and motor block onset times, time to first analgesic request, and DEX-related adverse effects were evaluated. Results were combined using fixed-effects or random effects modeling when appropriate., Findings: A total of 1478 patients from 25 clinical studies were included in the analysis. Compared with placebo, intrathecal DEX significantly prolonged the durations of both sensory block (weighted mean difference [WMD] = 134.42 min; 95% CI, 109.71-159.13 min; P < 0.001) and motor block (WMD = 114.27 min; 95% CI, 93.18-135.35 min; P < 0.001). It also hastened the onset of sensory block (WMD = -0.80 min; 95% CI, -1.21 to -0.40; P < 0.001) and motor block (WMD = -1.03 min; 95% CI, -1.51 to -0.56 min; P < 0.001). Furthermore, it delayed the time to first analgesic request (WMD = 216.90 min; 95% CI, 178.90-254.90 min; P < 0.001) and reduced the incidence of shivering (risk ratio [RR] = 0.39; 95% CI, 0.27-0.55; P < 0.001). DEX was associated with increased risk of transient bradycardia (RR = 1.59; 95% CI, 1.07-2.37; P = 0.022) and hypotension (RR = 1.40; 95% CI, 1.04-1.89; P = 0.026) but did not increase the incidence of postoperative nausea and vomiting (RR = 0.87; 95% CI, 0.62-1.24; P = 0.45)., Implications: Intrathecal DEX can prolong the duration of sensory block, the duration of motor block, and the time to first analgesic request associated with spinal anesthesia., Competing Interests: Disclosures The authors have indicated that they have no conflicts of interest regarding the content of this article., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)