Amitriptyline for chronic low back pain


Clinical question: Is a low-dose tricyclic antidepressant effective in the treatment of chronic low back pain?

Background: Lower back pain is the leading cause of disability globally and effective treatments are limited. Furthermore, opioid usage for lower back pain is a large contributor to the current opioid epidemic. A recent Cochrane review showed no clear evidence that antidepressant use in the treatment of back pain is effective, but it did note a lack of high-quality trials of sufficient rigor or length.

Study design: Double-blind, randomized controlled trial.

Setting: Single center trial in Melbourne.

Synopsis: Overall, 146 patients aged 18-75 with chronic lower back pain of no specific cause for more than 3 months were included. Exclusions included pathological cause, major coexisting illness, psychosis, or diagnosed depression. Patients were given amitriptyline 25 mg daily or benztropine mesylate 1 mg daily. Benztropine has similar anticholinergic side effects, without the antidepressant effect. Participants were assessed and followed by calls at 2 weeks, 1-2 months, 3 months, 4-5 months, and 6 months. Adherence was noted by the return of empty medication bottles at 6 months. Six-month surveys were completed by 81% and found that 70% of each group was adherent and 12% in each group withdrew because of adverse effects.

The primary outcome was level of pain at 6 months using a visual analog and descriptor scales. Secondary outcomes were measurement of disability, work missed, global improvement, general health, fear of movement, and depression.

The primary outcome was reduction in pain intensity of 12.6 (standard error, 2.7) with amitriptyline at 6 months, compared with 4.8 (SE 2.9) with benztropine, which did not meet statistical significance. There was a statistically significant difference in disability at 3 months, but not at 6 months.

Bottom line: This trial suggests that there may be a place for prescribed amitriptyline for chronic lower back pain, but it failed to show statistical significance. The study may not have been sufficiently powered to detect the difference.

Citations: Urquhart DM et al. Efficacy of low-dose amitriptyline for chronic low back pain: A randomized clinical trial. JAMA Intern Med. 2018;178(11):1474-81.

Dr. Lennon is an instructor of medicine at Northwestern University Feinberg School of Medicine and a hospitalist at Northwestern Memorial Hospital, both in Chicago.

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