It's nice of WebMD to print at the least the outcome parts of this. It isn't the only study out there. I've used Dextromethorphan-Polistirex for about 2 years now as needed, the main draw back is that it can cause memory problems *(as can all NMDA antagonist drugs including Topamax, Ketamine..etc). I never felt that they did as much as I wanted when they weren't combined with an opioid for fibro pain, but they finally looked at it without additional pain killers and still found a moderate benefit.

Two notes, Dextromethorphan reacts badly with SSRI/SNRI antidepressants and pretty much the entire range of psychiatric type medications, so check with your pharmacist with what you are taking.

The same chemicals involved in pain memory are also involved in storing regular memory, both long & short term. They are hoping to find subtypes in the receptors so that they can bypass this side effect. It isn't severe with Detromethorphan at low doses, but it can be severe with drugs like Ketamine. On the bright side, turning off the NMDA receptors cuts down on atrophic changes in the nervous system, they use it in stroke patients to limit the damage for this reason, for the same reason it might be useful in preventing some of the atrophic changes that happen in chronic pain.

http://my.webmd.com/content/article/106/108142.htm

(Heavly edited and condensed quote) May 23, 2005 -- An ingredient found in over-the-counter cough medicines may help ease the pain of fibromyalgia, according to new research from the University of Florida.

Fibromyalgia patients who took dextromethorphan experienced temporary reductions in the intensity of pain associated with minor repetitive physical contact -- a common characteristic of the poorly understood disease.

Researchers say the findings may have broader implications for the treatment of a host of chronic pain conditions.

Dextromethorphan has been shown to block the action of chemicals that relay pain to the spinal cord. It works by blocking a receptor known as N-methyl-D-aspartate or NMDA, which responds to these pain-transmitting chemicals. For this reason, Staud and colleagues evaluated the drug for pain control in fibromyalgia.

They found that people with fibromyalgia treated with dextromethorphan experienced moderate improvement in pain associated with repeated physical contact compared with those who got placebo treatments.

Better Drugs Needed

Staud tells WebMD that pharmaceutical researchers are working to develop more effective drugs that target the NMDA receptor with fewer side effects than the medications that are now available.

He estimates that these drugs could be commercially available within three to five years and could eventually be major players in pain control.

NMDA-receptor blockers like dextromethorphan have already been shown to improve pain control when given with morphine and other widely used opium-based medications. The hope is that combining the two drugs will allow a lower dose of the opioids to be used to control pain.