ARTHRITIS
May 26, 2012

Antidepressants to Relieve Pain

Duloxetine (Cymbalta) can help ease arthritis pain, though few patients receive it. Some experience side effects.

Antidepressant medications may provide as much pain relief for people with arthritis as the more commonly prescribed anti-inflammatory medications (NSAIDs) do. That's the conclusion of a recently published review.

The antidepressant duloxetine (better known as Cymbalta) was approved by the FDA for treating chronic pain in 2010 based on two studies showing that it was about as effective a pain treatment as NSAIDs are. But so far, few patients are receiving it as a treatment for pain.

Based on self-reported pain relief, about one patient out of six benefited from duloxetine treatment.

The review authors focused on these two studies of duloxetine as sole treatment for pain from osteoarthritis and a third that looked at duloxetine as an add-on treatment for people already taking an NSAID for knee osteoarthritis.

The two studies of duloxetine as stand-alone pain reliever for arthritis were 13-week randomized studies comparing pain relief of duloxetine to placebo. Based on self-reported pain relief, about one patient out of six benefited from duloxetine treatment.

This is similar to the treatment benefits found in previous reviews of two NSAIDs, etodolac (one in five patients) and tenoxicam (one in four patients), indicating that duloxetine is roughly as effective at treating pain as these other two medications.

That duloxetine isn't a magic bullet is shown by the number of people in these two studies who suffered from side effects: 16.3% of the subjects taking it discontinued treatment due to an adverse reaction. The three most common were nausea, fatigue and constipation. Only 5.6% of those taking placebo discontinued the study due to side effects.

Overall, after subtracting out the effects from placebo, one in six patients benefited and one in ten experienced significant side effects from duloxetine.

The reviewers also looked at a more recent study, a randomized trial of 524 people with knee arthritis whose pain had persisted despite taking an NSAID for it. All continued to take an NSAID, mainly ibuprofen or naproxen, while half also began to take duloxetine and the other half took a placebo.

After eight weeks, 35% who took duloxetine reported pain reduction of 50% or greater compared to 16% in the group taking placebo. Subtracting out the results from the placebo, these numbers indicate that nearly one in five patients (19%) experienced 50% or better pain relief from duloxetine.

Once again, discontinuation due to side effects was roughly one in six in the duloxetine group (15.2%), compared to 8.8% in the placebo group. Subtracting out side effects from placebo, this suggests that about one in sixteen patients experienced significant side effects from duloxetine.

Taken together, all three studies suggest that about one in six people with arthritis would benefit from taking duloxetine, alone or in combination with other medication. Considering how hard it is to effectively treat arthritis pain, the authors conclude that doctors treating patients with arthritis pain should consider prescribing antidepressants to them.

The review was published online before print by the International Journal of Clinical Practice.

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