Efficacy and safety of diclofenac in osteoarthritis: Results of a network meta-analysis of unpublished legacy studies

Abstract

Background and aim: Diclofenac is widely prescribed for the treatment of pain. Several network meta-analyses (NMA), largely of published trials have evaluated the efficacy, tolerability, and safety of non-steroidal anti-inflammatory drugs (NSAIDs). The present NMA extends these analyses to unpublished older (legacy) diclofenac trials.

Methods: We identified randomised controlled trials (RCTs) of diclofenac with planned study duration of at least 4 weeks for the treatment of osteoarthritis (OA) from 'legacy' studies conducted by Novartis but not published in a peer reviewed journal or included in any previous pooled analyses. All studies reporting efficacy and/or safety of treatment with diclofenac or other active therapies or placebo were included. We used a Bayesian NMA model, and estimated relative treatment effects between pairwise treatments. Main outcomes included pain relief measured using visual analogue scale at 2, 4 and 12 weeks and patient global assessment (PGA) at 4 and 12 weeks for efficacy, all-cause withdrawals, and adverse events.

Results: A total of 19 RCTs (5030 patients) were included; 18 of which were double-blind and one single-blind. All studies were conducted before cyclooxygenase 2 inhibitors (COXIBs) became commercially available. Data permitted robust efficacy comparison between diclofenac and ibuprofen, but the amount of data for other comparators was limited. Diclofenac 150mg/day was more efficacious than ibuprofen 1200mg/day and had likely favourable outcomes for pain relief compared to ibuprofen 2400mg/day. Diclofenac 100mg/day had likely favourable outcomes compared to ibuprofen 1200mg/day in alleviating pain. Based on PGA, diclofenac 150mg/day was more efficacious and likely to be favourable than ibuprofen 1200mg/day and 2400mg/day, respectively. Risk of withdrawal due to all causes with diclofenac and ibuprofen were comparable. Diclofenac 150mg/day was likely to have favourable efficacy and comparable tolerability with diclofenac 100mg/day. Results comparing diclofenac and ibuprofen were similar to those from NMAs of published trials.

Conclusions: Results from these unpublished 'legacy' studies were similar to those from NMAs of published trials. The favourable efficacy results of diclofenac compared to ibuprofen expand the amount of available evidence comparing these two NSAIDs. The overall benefit-risk profile of diclofenac was comparable to that of ibuprofen in OA.

Implications: The present NMA results reassures that the older unpublished blinded trials have similar results compared to more recently published trials and also contributes to increase the transparency of clinical trials performed with diclofenac further back in the past.

Keywords: Bayesian network meta-analysis; Diclofenac; Ibuprofen; Osteoarthritis; Patient global assessment; Randomised controlled trials; Visual analogue scale.