Opiates Create Pain – A New Pathway Mediated by Microglia


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Though morphine and other opiates are the gold standard for producing analgesia, paradoxically they may create pain.

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The mechanism, a microglia-to-neuron pathway in the spinal cord, has now been discovered by Ferrini et al. It was published in the on-line edition of Nature Neuroscience

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“Morphine hyperalgesia gated through microglia-mediated

disruption of neuronal Cl homeostasis.”

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Their research was reviewed January 8 in Medical News Today, exerpted below:

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….”Our research identifies a molecular pathway by which morphine can increase pain, and suggests potential new ways to make morphine effective for more patients,” says senior author Dr. Yves De Koninck, Professor at Université Laval in Quebec City. The team included researchers from The Hospital for Sick Children (SickKids) in Toronto, the Institut universitaire en santé mentale de Québec, the US and Italy.

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New pathway in pain management

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The research not only identifies a target pathway to suppress morphine-induced pain but teases apart the pain hypersensitivity caused by morphine from tolerance to morphine, two phenomena previously considered to be caused by the same mechanisms.

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“When morphine doesn’t reduce pain adequately the tendency is to increase the dosage. If a higher dosage produces pain relief, this is the classic picture of morphine tolerance, which is very well known. But sometimes increasing the morphine can, paradoxically, makes the pain worse,” explains co-author Dr. Michael Salter. Dr. Salter is Senior Scientist and Head of Neurosciences & Mental Health at SickKids, Professor of Physiology at University of Toronto, and Canada Research Chair in Neuroplasticity and Pain.

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“Pain experts have thought tolerance and hypersensitivity (or hyperalgesia) are simply different reflections of the same response,” says Dr. De Koninck, “but we discovered that cellular and signalling processes for morphine tolerance are very different from those of morphine-induced pain.”

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Dr. Salter adds, “We identified specialized cells – known as microglia – in the spinal cord as the culprit behind morphine-induced pain hypersensitivity. When morphine acts on certain receptors in microglia, it triggers the cascade of events that ultimately increase, rather than decrease, activity of the pain-transmitting nerve cells.”

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The researchers also identified the molecule responsible for this side effect of morphine. “It’s a protein called KCC2, which regulates the transport of chloride ions and the proper control of sensory signals to the brain,” explains Dr. De Koninck. “Morphine inhibits the activity of this protein, causing abnormal pain perception. By restoring normal KCC2 activity we could potentially prevent pain hypersensitivity.” Dr. De Koninck and researchers at Université Laval are testing new molecules capable of preserving KCC2 functions and thus preventing hyperalgesia.

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The KCC2 pathway appears to apply to short-term as well as to long-term morphine administration, says Dr. De Koninck. “Thus, we have the foundation for new strategies to improve the treatment of post-operative as well as chronic pain.”

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Dr. Salter adds, “Our discovery could have a major impact on individuals with various types of intractable pain, such as that associated with cancer or nerve damage, who have stopped morphine or other opiate medications because of pain hypersensitivity.”

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Cost of pain

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Pain has been labelled the silent health crisis, afflicting tens of millions of people worldwide. Pain has a profound negative effect on the quality of human life. Pain affects nearly all aspects of human existence, with untreated or under-treated pain being the most common cause of disability. The Canadian Pain Society estimates that chronic pain affects at least one in five Canadians and costs Canada $55-60 billion per year, including health care expenses and lost productivity.

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“People with incapacitating pain may be left with no alternatives when our most powerful medications intensify their suffering,” says Dr. De Koninck, who is also Director of Cellular and Molecular Neuroscience at Institut universitaire en santé mentale de Québec.

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Dr. Salter adds, “Pain interferes with many aspects of an individual’s life. Too often, patients with chronic pain feel abandoned and stigmatized. Among the many burdens on individuals and their families, chronic pain is linked to increased risk of suicide. The burden of chronic pain affects children and teens as well as adults.” These risks affect individuals with many types of pain, ranging from migraine and carpel-tunnel syndrome to cancer, AIDS, diabetes, traumatic injuries, Parkinson’s disease and dozens of other conditions.”

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The material on this site is for informational purposes only, and is not a substitute for

medical advice, diagnosis or treatment provided by a qualified health care provider.

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Please understand that it is not legal for me to give medical advice without a consultation.

If you wish an appointment, please telephone my office or contact your local psychiatrist.

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For My Home Page, click here:  Welcome to my Weblog on Pain Management!

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RSD/CRPS, Multiple Sclerosis, LDN & Ketamine


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It is rare for me to see a patient who is not complex.

They have failed so many treatments for so many years before they call.

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This is the report of a lovely woman in her early 70’s with progressive Multiple Sclerosis for 30 years and paraplegia that has forced her to use an electric scooter the last 5 years, and power wheelchair the last 2o years. Because of total paralysis of the right lower limb, she fell and shattered her femur, the thigh bone, in August 2009. Tragically, and all too often, the surgeon failed to diagnose Complex Regional Pain Syndrome [CRPS], even failed to visit her in the hospital. CRPS increased the fatigue she had already had from Multiple Sclerosis.

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Thankfully a physical therapist suggested the diagnosis.

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Why is pain management not a required subject for physicians?

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I have written elsewhere that the American Pain Society discovered that our National Institute of Health, NIH, devotes less than half of 1% of their research dollar to pain research. Of 28 NIH institutes, none for pain, three for addiction. This will not change soon. The only hope is that RSDSA.org will succeed in collaborating with all pain organizations, groups with dystonia, chronic fatigue in order to give a voice and research dollar to advances.

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Before seeing me in September, she had 11 sympathetic blocks with no benefit.

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Does it make you wonder why 11 were done?

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How does insurance authorize 11 when 10 had no benefit? I have just learned that a doctor must indicate at least 50% relief before another will be authorized. That explains it.

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Then she was given opioids including tramadal and Butrans patch which rendered her a “zombie,” sedated, poor memory, unable to function. She tried 4 or 5 treatments of Calmare with no benefit but was advised she needed a clear neural pathway for it to work. That was not possible due to the Multiple Sclerosis.
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Lyrica caused severe edema. Gabapentin 1400 mg/day caused weight gain, increased her appetite  more than usual, but she remained on it. She craves sweets more than usual, at times uncontrollably. Perhaps it can be slowly tapered now. Advil 600 mg gave some benefit but caused ulcers that required Nexium.

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Since her initial visit a few weeks ago, she became 60% better during her two week stay.

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I will highlight only two of the new medications started.

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It may also be said that opioids are not the answer.

Opioids may perpetuate pain.
They may produce paradoxical pain or opioid induced hyperalgesia or windup.

They may block the effect of ketamine and other adjuvants that would otherwise lower pain.

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Of importance is that she was not able to tolerate clothing on her right lower limb for three years, not even a sheet, and now she is able to sleep through the night without pain for the first time in three years and able to wear a skirt. This allows her to go out with family to restaurants and even to enjoy shopping with her daughter. Her dose of ketamine is very small relative to most of my patients and she uses it only once or twice a day since most of the new medications have brought her pain down.

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At her first visit one month ago, she rated pain from 6 to 8 on a scale of 10, average 7/10. Now 60% better, ranging from zero to 7, average 4. Yes zero pain, sleeping through the night without pain and waking without pain. She had not been able to tolerate touch to the right thigh or foot and would pull her skirt above the thigh, removing her shoe.

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Now she indicates pain continues to improve.

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Of interest, despite an abundance of concern that low dose naltrexone [LDN] may flare her Multiple Sclerosis, we were easily able to increase the dose to triple what is usually called “LDN.” This did not flare her condition and may be one of the most effective medications she is taking for pain.

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What is LDN?

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The FDA has sanctioned its use in the USA only in doses of 50 to 400 mg for addiction to opioids and alcohol.

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Low dose naltrexone [LDN] is a fascinating medication. It has been used in low dose in persons with Multiple Sclerosis since 1985 when a Harvard trained neurologist in New York City, Dr. Bihari, first discovered that it relieved all disability in some patients with Multiple Sclerosis and prevented recurrent attacks. Since then, doctors in Scotland, where they have the highest incidence of Multiple Sclerosis, find that one of the earliest signs of recovery in this population is relief of neurogenic bladder. It is said that persons with Multiple Sclerosis must remain on LDN for 1.5 years before they might fully assess its value.

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 Multiple Sclerosis may be flared unless very small doses of LDN are used.

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Many with Mulitple Sclerosis cannot tolerate more than 2 or 3 mg, perhaps due to spasticity. There is a great deal of dogma on the web about its mechanism, dosing and timing for off label use. Use the search function on this site to review the prior discussions I posted on LDN, MS, CRPS.

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Naltrexone is a glial modulator.

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What’s that?!

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By serendipity, four years ago I discovered naltrexone in low dose may relieve chronic intractable pain. I had been using it for perhaps eight years in microgram doses but I found in milligram doses it is even more profound.

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The mechanism of naltrexone and a wee bit of glial research is discussed here. The Nobel Prize was awarded last year for the discovery that these glia are your innate immune system. They are profoundly important in many diseases including chronic pain, Major Depression, Multiple Sclerosis, Alzheimers, Parkinsons Disease, ALS, Autism. They produce inflammatory cytokines that lead to inflammation.

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Now that she has been home for two weeks, on a number of medications that I started, not just the ketamine and LDN, I hope she will comment on her experience and her progress since flying back to the east coast after her brief visit here.

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It is often essential to taper off opioids to allow other medication to work.

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I feel she was able to benefit from these low doses of medication because she tapered off all opioid medication prior to her visit, thus allowing her system to recover and respond to these medications. We will know more in the next few months as she slowly titrates up on some of the medications that were started.

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Next year on her return, we may be able to withdraw some of the medications depending on how well she is doing.

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Finally, ketamine does cause her to have brief side effects. Her husband likens the effect the same as half a glass of wine: “She’s really cute.” Thankfully, most people have no side effects and if they do, they rarely last more than 20 minutes.

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She sends an update below, 80 to 90% better. Hopefully this will continue to improve over the next months as she slowly increases the medication we started. And ketamine has an additive effect in some. It is anti-inflammatory.

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The material on this site is for informational purposes only.

It is not a substitute for medical advice, diagnosis or treatment provided by a qualified health care provider.

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Please understand that it is not legal for me to give medical advice without a consultation.

If you wish an appointment, please telephone my office or contact your local psychiatrist.

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For My Home Page, click here:  Welcome to my Weblog on Pain Management!

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Gliopathic Pain — when Neuropathic Pain Treatment Fails


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Coming soon, though these stand on their own:

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Modulation of microglia can attenuate neuropathic pain symptoms and enhance morphine effectiveness.

Abstract

Microglia play a crucial role in the maintenance of neuronal homeostasis in the central nervous system, and microglia production of immune factors is believed to play an important role in nociceptive transmission. There is increasing evidence that uncontrolled activation of microglial cells under neuropathic pain conditions induces the release of proinflammatory cytokines (interleukin – IL-1beta, IL-6, tumor necrosis factor – TNF-alpha), complement components (C1q, C3, C4, C5, C5a) and other substances that facilitate pain transmission. Additionally, microglia activation can lead to altered activity of opioid systems and neuropathic pain is characterized by resistance to morphine. Pharmacological attenuation of glial activation represents a novel approach for controlling neuropathic pain. It has been found that propentofylline, pentoxifylline, fluorocitrate and minocycline decrease microglial activation and inhibit proinflammatory cytokines, thereby suppressing the development of neuropathic pain. The results of many studies support the idea that modulation of glial and neuroimmune activation may be a potential therapeutic mechanism for enhancement of morphine analgesia. Researchers and pharmacological companies have embarked on a new approach to the control of microglial activity, which is to search for substances that activate anti-inflammatory cytokines like IL-10. IL-10 is very interesting since it reduces allodynia and hyperalgesia by suppressing the production and activity of TNF-alpha, IL-1beta and IL-6. Some glial inhibitors, which are safe and clinically well tolerated, are potential useful agents for treatment of neuropathic pain and for the prevention of tolerance to morphine analgesia. Targeting glial activation is a clinically promising method for treatment of neuropathic pain.

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Microglia: a promising target for treating neuropathic and postoperative pain, and morphine tolerance.

Source

Department of Anesthesiology, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, USA.

Abstract

Management of chronic pain, such as nerve-injury-induced neuropathic pain associated with diabetic neuropathy, viral infection, and cancer, is a real clinical challenge. Major surgeries, such as breast and thoracic surgery, leg amputation, and coronary artery bypass surgery, also lead to chronic pain in 10-50% of individuals after acute postoperative pain, partly due to surgery-induced nerve injury. Current treatments mainly focus on blocking neurotransmission in the pain pathway and have only resulted in limited success. Ironically, chronic opioid exposure might lead to paradoxical pain. Development of effective therapeutic strategies requires a better understanding of cellular mechanisms underlying the pathogenesis of neuropathic pain. Progress in pain research points to an important role of microglial cells in the development of chronic pain. Spinal cord microglia are strongly activated after nerve injury, surgical incision, and chronic opioid exposure. Increasing evidence suggests that, under all these conditions, the activated microglia not only exhibit increased expression of microglial markers CD 11 b and Iba 1, but also display elevated phosphorylation of p38 mitogen-activated protein kinase. Inhibition of spinal cord p38 has been shown to attenuate neuropathic and postoperative pain, as well as morphine-induced antinociceptive tolerance. Activation of p38 in spinal microglia results in increased synthesis and release of the neurotrophin brain-derived neurotrophic factor and the proinflammatory cytokines interleukin-1β, interleukin-6, and tumor necrosis factor-α. These microglia-released mediators can powerfully modulate spinal cord synaptic transmission, leading to increased excitability of dorsal horn neurons, that is, central sensitization, partly via suppressing inhibitory synaptic transmission. Here, we review studies that support the pronociceptive role of microglia in conditions of neuropathic and postoperative pain and opioid tolerance. We conclude that targeting microglial signaling might lead to more effective treatments for devastating chronic pain after diabetic neuropathy, viral infection, cancer, and major surgeries, partly via improving the analgesic efficacy of opioids.

 

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The material on this site is for informational purposes only, and is not a substitute for medical advice,
diagnosis or treatment provided by a qualified health care provider.
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For My Home Page, click here:  
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