Opioids: No Tolerance for Inflammation!

The news on painkillers like morphine and Oxycontin just keeps getting more exciting. A new study highlighted here suggests that when pain is caused by inflammation, tolerance to opioids is less likely to develop. In a model of inflammatory pain in rats, researchers found that the same dose of morphine continued to provide consistent relief.

The rats had pain from chronic inflammation in their paws. However, when opioid receptors in the paws were blocked, tolerance did later develop, showing that inflammation itself somehow prevents the development of tolerance, at least in the peripheral nerves.

This means that patients with conditions like multiple sclerosis, rheumatoid arthritis and cancer don't have to worry so much that opioid drugs will "stop working" and that they will constantly have to chase tolerance. As long as the underlying pain itself doesn't get worse, the drugs should continue to work.

Clinicians who work with patients themselves have long suspected that this was the case in many pain disorders. Now, there's animal data to support them.

Ironically, many doctors believe that opioids are not useful for what is known as "neuropathic" pain-- pain due to nerve damage, which is often associated with inflammation. But other research suggests that this, too, is a myth.

Now if only the rest of the misinformation and fear that so often surrounds opioids could be put to bed, too.