Abstract Background To examine the response to an α2receptor agonist used as a sedative for patients using long-term selective α1 blockers. Methods Sixty-nine consecutive patients undergoing transurethral prostate resection or holmium laser resection of the prostateunder spinal anesthesia were divided into two groups; group N (n = 37), which did not receive α1 blockers, and group T (n = 32), which was administered tamsulosin for at least 1 month before the study. Bispectral index scores, Modified Observer’s Assessment of Alertness/Sedation scale scores, heart rate, and mean blood pressure were obtained under sedation using dexmedetomidine for 30 min during surgery. Results The only significant difference found between the groups were mean bloodpressure 15 min after the first loading dose injection of dexmedetomidine. Differencesbetween both groupswere noted at 15 min(group T: 100.2 ± 12.9 mmHg; group N: 90.0 ± 17.5 mmHg; P = 0.08), 20 min (group T: 99.8 ± 12.3 mmHg; group N: 87.4 ± 15.0 mmHg; P