A phase III, randomized, double blind, controlled trial to evaluate the efficacy and safety of a fixed combination of intramuscular diclofenac 75 mg + thiocolchicoside 4 mg, compared to diclofenac 75 mg monotherapy and placebo, in the treatment of acute low back pain.

Abstract

Background: This study aimed to demonstrate the superiority of diclofenac sodium 75 mg/thiocolchicoside 4 mg/4 mL fixed-dose combination (FDC) for intramuscular (IM) injection vs. diclofenac 75 mg alone or placebo in relieving pain in patients suffering from low back pain (LBP).

Methods: Adult patients with acute moderate-severe LBP, i.e., with ≥50 mm at Visual Analogic Scale (VAS) assessment and stable muscle contracture, were randomized to receive diclofenac/thiocolchicoside FDC (N.=68), diclofenac monotherapy (N.=68) or placebo (N.=69), all given IM once-daily in two consecutive days. The primary endpoint was the sum of pain intensity difference from pre-dose to Day 3 in VAS for pain - SPID(0-3). Pain was also measured twice daily up to Day 7.

Results: Mean SPID(0-3) was significantly higher with test FDC (116.2 mm) versus diclofenac (94.8 mm) and placebo (62.6 mm). The superiority of FDC over control groups was maintained up to Day 7 - SPID(0-7). Muscle contracture (expressed as Schober's index) decreased more markedly in the test group compared to controls. The results of the 24-item Roland-Morris disability questionnaire confirmed the superiority of FDC over diclofenac and placebo on physical functions. Rescue treatment (oral diclofenac) was used in fewer patients in the FDC group than in control groups. Treatment-related adverse events were reported in fewer patients in the FDC and diclofenac groups (5.9%) compared to the placebo group (16.2%).

Conclusions: IM diclofenac + thiocolchicoside FDC was significantly more effective than diclofenac and placebo in the relief of pain and improvement of mobility in patients with acute moderate-severe LBP, and was well tolerated.