The aim of the study was to evaluate the analgesic effect of metamizole sodium administered intravenously during the day after surgery in patients operated on for nodular goitre - using the 11-point NAS scale (Numeric Analog Scale).Material and methods. The study was comprised of 114 patients who had undergone surgery for nontoxic: 84 (73.7%) or toxic: 30 (26.3%) nodular goitre. The goitre size, according to the WHO classification ranged between III and I° (2). I° goitre was found in 31 (27%) patients, II° goitre - in 46 (40.4%) patients and III° goitre - in 37 (32.4%) patients. The age of patients ranged between 22 and 75 years (median 53, IQR 43-61). The goitre was localized in the neck in 103 (90.4%) patients and it partially reached the superior aperture of the thorax with its lower poles in 11 (9.6%) patients. Patients with coexisting diseases such as diabetes mellitus or peripheral neuropathy were excluded from the study. Patients were randomly assigned to 4 groups. Group I included 38 subjects in whom metamizole sodium was applied at a dose of 1 g intravenously every 6 hours for a day after surgery; the first dose was administered at the moment of surgical wound closure. Group II included 37 patients in whom metamizole sodium was applied according to the above-mentioned regimen and, additionally the surgical wound was injected with 10 ml of bupivacaine 0.25%. Group III consisted of 36 patients in whom 1 g of metamizole was first administered intravenously thirty minutes before surgery and the subsequent doses were systematically repeated at time intervals of 6 hours (preemptive analgesia), avoiding buvacaine wound infiltration. Group IV included 40 patients in whom ketoprophen was administered intravenously at a dose of 0.1 g every 6 hours for a day after the procedure. Surgical wounds were not injected with buvacaine in these patients, similarly as in groups III and I. In case of severe pain patients could additionally receive morphine 1 mg on-demand.Results. Pain intensity was analyzed every 6 hours on NAS scale and pain scores ranged from 1 to 5.5. At all time points, the highest pain intensity scores were found in patients who received metamizole as monotherapy (group I) or ketoprofen (group IV), while the lowest were found in the groups where surgical wound was additionally injected with bupivacaine solution (group II) or additional metamizole dose was used before the procedure (group III). Patients from group II rated their pain intensity as slightly higher or similar to that in group III (statistically insiginficant). Similarly patients from group I had pain scores slightly higher or similar to scores reported in group IV (statistically insiginficant).Conclusions. 1. The most intense pain was observed during the first 12 hours after thyroid surgery. 2. Administration of metamizole sodium according to the regimen that was applied in groups II and III provided sufficient analgesia. 3. Infiltration of the surgical wound with buvacaine or administration of an additional dose of metamizole sodium prior to the surgery (preemptive analgesia) results in postoperative pain relief and allows avoiding demand for opioid analgetics.