Slow injection of nefopam reduces pain intensity associated with intravenous injection: a prospective randomized trial

Abstract

We aimed to investigate the frequency and severity of pain associated with intravenous injection of nefopam and to determine whether a slow rate of administration can effectively reduce such pain. We used a solution containing 30 mg nefopam diluted to 20 ml in saline. In all, 102 adult patients undergoing minor surgery were randomly allocated to one of three administration groups: A (60 ml/h, n = 34); B (120 ml/h, n = 34); or C (180 ml/h, n = 34). All patients scored the maximal pain experienced during the 120-s infusion period, using the visual analogue scale (VAS) and the verbal pain score (VPS). Adverse events including phlebitis were recorded. Eighty-three patients (29 in group A, 27 each in groups B and C) were included in the final analysis. The incidence of injection pain was lower in group A (86.2 %) than in groups B (96.3 %) and C (100 %), but this difference was not statistically significant. The proportion of patients with a tolerable level of pain (VAS 0-3 and VPS 0-1) was significantly higher in group A (79.3 %) versus groups B (7.4 %) and C (3.7 %). The mean VAS scores for groups A, B, and C were 2.2 +/- A 1.3, 5.1 +/- A 1.6, and 7.2 +/- A 1.7, respectively, and these differences were statistically significant. At the slower rate of infusion (60 ml/h) of the 1.5 mg/ml nefopam solution, injection pain intensity was attenuated to a significantly greater degree than at the faster rates.