Objective: To evaluate analgesic efficacy and safety/tolerability of the nonbenzodiazepine antispasmodic pridinol (PRI) in patients with muscle-related pain.

Methods: Systematic review and meta-analysis of randomized placebo-controlled trials (RCTs) according to PRISMA guidelines and Cochrane recommendations. Data sources included Google Scholar, Embase, PubMed, ClinicalTrials.gov, EU Clinical Trials Registry, Chinese Clinical Trial Registry, UMIN Clinical Trials Registry, and product manufacturer archives from inception to 31 January 2022. Eligibility criteria for study selection were randomized, placebo-controlled trials with PRI in adults (≥18 years) with muscle-related pain. Data extraction, synthesis, and analysis carried out by two reviewers independently identified studies, extracted data, and assessed the risk of bias using the Cochrane risk of bias tool. Categorial global response rates (number of patients) based on clinical judgement of study physicians (as primary efficacy endpoint), and response on pain at rest, pain at movement, stiffness, tenderness, and movement restriction (as secondary efficacy endpoints), as well as the number of patients with drug-related adverse events (DRAEs) were meta-analytically evaluated using the Review Manager Software version 5.4.1.

Results: In total, 38 records were identified, but only two placebo-controlled studies (with 342 patients with mild to moderate acute muscle pain [55.3% female, age 50.6 ± 16.6 years], of whom 173 received PRI and 169 placebo, each as monotherapy) proved to be suitable for quantitative and qualitative analysis. Treatment with PRI was (irrespective of its mode of administration as oral tablet or intramuscular injection) associated with a significantly higher global response rate compared to placebo (74.0 vs. 49.7%; OR 2.86, 95%-CI: 1.82-4.51; p < .00001; Cohen´s h: 0.506, NNT: 4.1; Chi² for heterogeneity 1.41 (p = .24], I² = 29%), and significantly higher response rates were also found for all secondary efficacy endpoints. The safety of PRI was comparable to that of placebo: DRAEs were only seen in one of the two studies and reported for 13 vs. 10 patients (OR: 0.76 95%-CI: 0.32-18.1; p = .54, NNH: 62.6), and related discontinuations were reported for four vs. one patient (2.3 vs. 0.6%; p = .231).

Conclusions: The results from this meta-analysis as based on two placebo-controlled studies in adult patients with mild to moderate acute muscle pain demonstrate that a 3-week monotherapy with PRI showed a comparable safety profile, but significantly better analgesic effects and improvements of related impairments such as stiffness, tenderness, and movement restrictions compared with placebo - irrespective of its mode of administration.