Intramuscular versus oral diclofenac for acute pain in adults with acute musculoskeletal injuries presenting to the ED setting: a prospective, double-blind, double-dummy, randomised controlled trial.

OBJECTIVE: The current study aimed to ascertain differences in early postmedication pain reduction in participants presenting with acute musculoskeletal injuries (MSI) to the ED receiving intramuscular (IM) versus per oral (PO) diclofenac.

METHODS: This was a prospective, double-blinded, randomised controlled trial conducted between January and June 2018 at the ED of Hamad General Hospital in Doha, Qatar. Adults (18-65 years of age) presenting to the ED within 24 hours of an acute MSI, who had a triage pain score measured using numerical rating scale of at least five or above were enrolled in this trial. Participants randomised to either IM (75 mg) with oral placebo, or oral (100 mg) diclofenac group with IM placebo using a computer-generated randomised concealed list in blocks of six and eight. The primary objective was to compare the proportion of IM versus PO participants attaining a 50% reduction in pain score at 30 min from t0.

RESULTS: 300 participants were enrolled (150 in the IM diclofenac group and 150 in the PO diclofenac group) in the trial. The primary outcome was achieved in 99.3 (95% CI 96.3 to 100) in the IM group and 86.7 (95% CI 80.2 to 91.7) in PO group. There was an absolute risk difference of 12.7%. This corresponds to a number needed to treat of 8 cases (95% CI 6 to 14) receiving IM rather than the PO diclofenac in order to achieve one additional case of 50% pain reduction within 30 min of drug administration. There were no adverse events experienced in any treatment groups.

CONCLUSION: IM diclofenac injection provides rapid analgesia over PO administration of diclofenac. However, given the preparation needed for an IM injection, oral administration may be preferable when and if clinical circumstances allow a choice in non-steroidal anti-inflammatory drug administration route.