Is low-dose amitriptyline effective in the management of chronic low back pain? Study protocol for a randomised controlled trial

Low back pain is a major clinical and public health problem, with limited evidence-based treatments. Low-dose antidepressants are commonly used to treat pain in chronic low back pain. However, their efficacy is unproven. The aim of this pragmatic, double-blind, randomised, placebo-controlled trial is to determine whether low-dose amitriptyline (an antidepressant) is more effective than placebo in reducing pain in individuals with chronic low back pain. One hundred and fifty individuals with chronic low back pain will be recruited through hospital and private medical and allied health clinics, advertising in local media and posting of flyers in community locations. They will be randomly allocated to receive either low-dose amitriptyline (25 mg) or an active placebo (benztropine mesylate, 1 mg) for 6 months. The primary outcome measure of pain intensity will be assessed at baseline, 3 and 6 months using validated questionnaires. Secondary measures of self-reported low back disability, work absence and hindrance in the performance of paid/unpaid work will also be examined. Intention-to-treat analyses will be performed. This pragmatic, double-blind, randomised, placebo-controlled trial will provide evidence regarding the effectiveness of low-dose antidepressants compared with placebo in reducing pain, disability, work absenteeism and hindrance in work performance in individuals with chronic low back pain. This trial has major public health and clinical importance as it has the potential to provide an effective approach to the management of chronic low back pain. Australian New Zealand Clinical Trials Registry: ACTRN12612000131853 ; registered on 30 January 2012.