Introduction: During transurethral resection of the prostate (TURP), the most established surgical treatment of lower urinary tract symptoms (LUTS) due to benign prostatic obstruction (BPO), the prostate can bleed profusely, bringing about anaemia and compromised oxygen delivery to the entire body. Objective: The primary objective of this study was to assess the efficacy of mepivacaine and adrenaline (MA) injected into the prostate on bleeding. The primary endpoint was to measure blood loss per resected weight of prostate tissue. Material and methods: This randomised controlled trial evaluated 81 patients with LUTS/BPO. Patients were randomly allocated to regular TURP or TURP with intraprostatic injections of MA. Results: On univariable analyses there was a significant difference in resection weight in favour of the experimental group, not reflected by a statistically significant difference in the other studied outcome parameters. Nevertheless, in multivariable analyses, blood loss per resection weight, which was the primary outcome, showed a significant decrease in favour of the experimental group. Clavien-Dindo complication classification showed three men with a grade I complication and two men with grade II. Conclusions: The results obtained in this study showed that it is beneficial to apply intraprostatic injections of MA in immediate conjunction with TURP, in terms of blood loss per resected gram. The study is, however, small and corroboration of our results in more extensive prospective studies may therefore be warranted before embarking upon this technique.