Analgesic Efficacy and Tolerability of Amitriptyline versus Mianserin in Chronic Low Back Pain: A Randomised, Double-Blind, Controlled Pilot Trial

Abstract

Purpose: Chronic low back pain (CLBP) is a complex, disabling condition that often necessitates multimodal treatment. Although tricyclic and tetracyclic antidepressants are recommended as adjunctive therapy, comparative efficacy data remain extremely limited. Patients and Methods: We conducted a randomised, double-blind, controlled trial in 24 individuals with CLBP to compare the efficacy and safety of amitriptyline with mianserin. Participants received amitriptyline (n = 15) or mianserin (n = 9) for 12 weeks with titrated dosing. Pain intensity (primary outcome), adverse effects, disability, health utility, quality of life, and psychological function were recorded at baseline and at each follow-up visit. Results: Participants in both groups reported significant within-group reductions in pain intensity from baseline to week 12. Mianserin was associated with a large effect size improvement (Cohen’s d = −1.40; 95% CI −2.71 to –0.08), and amitriptyline was associated with a medium effect size improvement (d = −0.55; 95% CI −1.19 to 0.08). Amitriptyline significantly improved EQ-5D-5L utility scores (Δ=+0.116, p=0.008; d=0.61, 95% CI 0.14 to 1.09) but was associated with more anticholinergic effects than mianserin. Mianserin was better tolerated; only transient drowsiness was reported. Different benefits were noted in some outcome measures as a function of treatment condition: amitriptyline reduced stress by week 6, whereas mianserin lowered anxiety at weeks 6 and 12. Conclusion: Both amitriptyline and mianserin appear to provide comparable adjunctive efficacy for CLBP. Mianserin may be more tolerable and cost-effective in resource-limited settings, although it is not yet approved for pain indications.