Pain relief

A common antidepressant drug may provide an alternative for people suffering from chronic osteoarthritic knee pain

Every week Christchurch general practitioner Dr Ben Hudson sees patients with severe pain from osteoarthritis, but with few options for relief. Drugs currently available are either inadequately effective or cause unpleasant and dangerous side effects.

This common – and frustrating – medical situation provided the inspiration for Hudson's research project in his other job as a University of Otago, Christchurch (UOC) researcher and senior lecturer.

A common antidepressant drug may provide an alternative for people suffering from chronic osteoarthritic knee pain.

Hudson has been granted more than $1 million from the Health Research Council for a three-year research project on the effectiveness of the antidepressant drug nortriptyline in alleviating chronic pain caused by arthritis of the knee.

He says the idea behind the research is simple, but could have far-reaching implications for patients whose knee pain impedes simple activities such as walking.

“Nortriptyline is an interesting drug because it's been around for a few decades as an antidepressant drug, but has also been found to be successful in treating some chronic pain conditions such as nerve damage, post-shingles neuralgia and persistent back pain.

“Because of a lack of alternatives, some doctors have been prescribing nortriptyline out of desperation to patients with chronic pain from knee arthritis and it does seem effective. What we really need to know now is whether this effect is real and not due to a placebo effect.''

Hudson's study will test this effect by randomly allocating participants treatment with either nortriptyline or a placebo pill over a three-year period. Changes to patients' pain levels will be measured before and after periods on the medication. Patients will be recruited from the Canterbury District Health Board orthopaedics outpatients' department and general practices in Christchurch.

The head of the UOC's Department of General Practice, Professor Les Toop, and another senior researcher and GP from the department, Associate Professor Dee Mangin, will also work on the study.

Hudson says an advantage of nortriptyline is that it is a generically available drug. This means if the study shows nortriptyline reduces pain, it will be a cost-effective treatment for the common condition.

A study by UOC's Professor Gay Hooper, published in 2014, estimated demand for knee replacements will increase by 183 per cent by 2026. Hudson says there are already many patients with chronic osteoarthritis knee pain who do not meet the threshold for surgery. As demand for surgery increases, so will numbers of incapacitated patients who need pain relief without serious side effects.

“Persistent pain from osteoarthritis severely limits patients' mobility and their ability to live an active, enjoyable life. Because they struggle with mobility and often find walking difficult, they often gain weight and lose physical fitness. This puts more pressure on their knees and it becomes a vicious cycle. Hopefully this study could provide a safer, more effective way to manage that pain and make their lives a bit better.''