Low-dose tricyclic antidepressants (TCA) should be used instead of opioids for low back pain in an effort to avoid a US-style prescription opioid crisis, Australian researchers say
The first major randomised controlled trial (RCT) of a low-dose TCA in low back pain found that it had modest beneficial effects on pain and disability, sufficient to warrant consideration in place of an opioid, according to Monash University investigators.
In an RCT involving 146 adults with chronic low back pain, Dr Donna Urquhart (PhD) and colleagues in the university’s Department of Epidemiology and Preventive Medicine compared a regimen of 25mg daily amitriptyline with an active placebo, benztropine, for six months.
Benztropine was chosen as the comparator to aid blinding because it mimics the dry mouth effect of a tricyclic but with little therapeutic effect on pain or disability.
Amitriptyline was associated with greater improvements in disability at three months compared to the control group and also showed reductions in pain intensity at six months that were of borderline significance (p = 0.05).
However, there was little overall difference between the tricyclic antidepressant and comparator groups in the main outcomes of pain and disability at three and six months. The TCA was no different to placebo in effects on measures of work absence or hindrance, and global measures of health, and was also similar to placebo in rates of adverse events.
Writing in JAMA Internal Medicine Dr Urquhuart and colleagues note that TCAs are already recommended in many guidelines for management of low back pain, although the recommendations vary widely in terms of dose, and recommendations are not based on robust studies.
“The present trial aimed to address these limitations, namely, the lack of investigation of low-dose antidepressants for pain, insufficient blinding and statistical power, and short treatment and follow-up periods,” they say.
Since the trial showed that amitriptyline provides some benefit and is well tolerated in low back pain, this suggests that large-scale clinical trials that include dose escalation are needed, they add.
“This finding is important given that low back pain is the leading cause of disability globally, effective treatments … are limited, and there is currently an epidemic of escalated usage of narcotics, with more than 50% of narcotic prescriptions issued to people with low back pain.
“In the meantime, it may be worth trying low-dose amitriptyline for these patients, especially if the only alternative is an opioid,” they conclude.
PBS figures show there were almost half a million (498,790) prescriptions for amitriptyline 25mg in 2016/17, up from a level of around 400,000 in 2006-7.