This study aimed to evaluate whether diphenhydramine hydrochloride (DPH) could be used to reduce the dose of lidocaine for intravenous regional anaesthesia (IVRA). Sixty patients undergoing upper limb operations were divided into three groups (20 each). All patients received IVRA as follows: group 1 received 3 mg/kg lidocaine, group 2 received 40 mg DPH and 1.5 mg/kg lidocaine, and group 3 received 1.5 mg/kg lidocaine diluted to 40 ml with 0.9% saline solution. The onset of sensory block was tested by a pinprick. The duration of anaesthesia time was also recorded. Intraoperative pain was assessed using a five point pain score system. Side effects during surgery and after release of the tourniquet were recorded. Only 4 patients in group 3 had sufficient analgesia. Therefore, the patients in group 3 were excluded from the study. Data from 40 patients (group 1 and 2) were analysed. The onset time of sensory block was significantly shorter in group 1 than group 2 (2.4 ± 1.54 min and 6.85 ± 1.46 min, respectively). The tourniquet pain time was also significantly longer in group 1 than in group 2 (57.15 ± 10.90 min and 42.65 ± 9.67 min, respectively). One patient from each group experienced tinnitus for 30-60 s, and 4 patients in group 2 had minimal sedation after tourniquet release. According to our results, DPH is a safe and useful adjunct to IVRA in minor procedures of short duration. Decreasing the dose of lidocaine also decreases the risk of local anaesthetic toxicity in the event of accidental release of tourniquet pressure.