Fibromyalgia Syndrome (FMS) Archives

Acetaminophen

The BMJ (what used to be called the British Medical Journal) just published an article stating that acetaminophen (ie Tylenol) has been found to provide no relief in low back pain (compared to a placebo). Acetaminophen was also related to a risk of having an abnormal liver test. The article included data from 13 randomized controlled trials (RCTs).

An RCT to evaluate a drug is a research study where one group of people receives the actual drug (in this case, acetaminophen) and the other group receives a placebo (a pill with no active ingredient, generally a sugar pill). Then, data is collected from both groups to see if either achieved any painTylenol relief. In this analysis, it shows that whether you receive acetaminophen or a sugar pill, you had the same amount of pain relief – meaning that active drug had no real pain relief effect.

Although most of the patients I see find no relief from acetaminophen, a small percentage of patients do, so don’t completely dismiss this drug when it comes to helping your pain. However, if you do take acetaminophen, make sure that you’re not taking too much. The FDA recommends taking less than 3000mg a day. This means if you’re taking Extra Strength Tylenol (500mg), you can only take 6 pills a day, or regular strength, 300mg, 10 pills a day. Higher amounts can lead to liver damage that could even be life-threatening.

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Conditioned Pain Modulation

Have you ever noticed that pain in one area took your attention away from pain in another spot?  For example, you were feeling back pain and then jammed your toe, and your back pain diminished or went away.  As the toe pain reduced, the back pain reappeared.  Conditioned Pain Modulation (CPM), formerly known as DNIC (diffuse noxious inhibitory control), is the phenomenon where pain in one area inhibits pain in a different area of the body.

Another example is seen in patients who have pain that is noticeably worse on one side of the body than the other.  Once pain is treated on their “bad” side, their “good” side seems to get much worse.  In this case, pain on the “good” side was always present, but becomes more noticeable once the worst pain was addressed.

In fibromyalgia syndrome patients, there appears to be impaired CPM. [i]  CPM is one reason why understanding a patient’s pain complaint is challenging.


[i] Davis, Mellar P. “The Clinical Importance of Conditioning Pain Modulation: A Review and Clinical Implications.” Research and Development of Opioid-Related Ligands (2013): n. pag. Print.

 

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We see that in some patients who have central sensitization, treating the peripheral pain generators may results in a decrease or elimination of the widespread pain.

Widespread pain is often addressed with medication. It is common for a patient to be given an anticonvulsant, such as pregabalin (Lyrica) or gabapentin (Neurontin), or a serotonin-norepinephrine reuptake inhibitors (SNRIs), such as duloxetine (Cymbalta) or venlafaxine (Effexor).  These drugs affect the neurons transmitting pain-related signals in the central nervous system.nerve bundle-Norman Marcus Pain Institute blog

Another possible target in the nervous system is the glial cells. The glia are non-neuronal cells that provide support and protection for the neurons.  90% of the central nervous system (spine and brain) are made up of glial cells.

Two cells types, microglia and astrocytes, recently have been found to play a role in pain processing. These two types of cells are stimulated in response to damaged or dying cells. Astrocytes produce inflammation, while microglia initiate both inflammatory and anti-inflammatory activity. An inflammatory response in the microglia results in pain-producing chemicals, adding to the patient’s overall pain. Chronic pain and opioids, such as morphine and oxycodone, can also stimulate the microglia to produce these same pain-producing chemicals.

This may be one of the reasons why opioids are ineffective in patients with long-standing pain, as with fibromyalgia (FMS). Interestingly, drugs that block opioids, such as naltrexone, in very small doses have been found to be effective in decreasing pain in FMS (http://www.ncbi.nlm.nih.gov/pubmed/23359310). The mechanism appears to be blocking the pain producing effect of the microglia. Since the doses are so small (~4mg/day), the typical blocking of the mu receptor (the receptor that is known to be typically stimulated by opioids) doesn’t occur. What we often find as a result is pain relief and a decreasing need for opioids.

Since microglia also play an anti-inflammatory  role, in our search for drugs to affect the microglia, we need to find a balance in which we can maintain their protective anti-inflammatory roles while also reducing their inflammatory pain producing effects.  (http://www.nature.com/nrn/journal/v10/n1/abs/nrn2533.html)

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Treating widespread pain vs. the original pain generator

hip joint-Norman Marcus Pain Institute blogConsidering the possible effects of central sensitization may affect the treatment plan (and in turn the outcome) for a patient in pain.

For example, take someone who injured a joint – let’s say a hip – which led to osteoarthritis and in addition diffuse, widespread hyperalgesia (increased sensitivity to pain). Sometimes when a patient is in pain for a long period of time, we concentrate on the widespread pain rather than the original pain generator, the hip. These patients may be diagnosed with fibromyalgia because of their widespread pain, with treatment concentrated on that diagnosis. If the hip is treated (for example, a hip replacement), the widespread pain may resolve. This was demonstrated in a recent article, published in May 2013, that studied 40 patients. Patients who received hip replacements had normalization of their increased sensitivity  and elimination of their widespread pain. (http://www.ncbi.nlm.nih.gov/pubmed/23400951)

Let’s take a look at a contrasting scenario in my next blog.

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More on Fibromyalgia Syndrome (FMS)

I reread my blog on misleading diagnoses and central sensitization, and it confused me, so it must have confused some of you.   The point was that if so many of us have different interpretations of pain and how to treat it, we can’t all be right.Nonspecific Low Back Pain-10-8-13

I want to discuss specific pain syndromes where it is unclear what causes the pain. We have batted around some causes and possible explanations for Nonspecific Low Back Pain. I want to explore Fibromyalgia Syndrome (FMS), a condition characterized by widespread, diffuse pain on both sides of the body, above and below the waist.  In order to be diagnosed with FMS, patients must experience pain at a minimum of 11 out of 18 specified tender points, stiffness in joints, extreme fatigue, and difficulty sleeping.  Due to the diffuse nature of FMS, it is often difficult to pinpoint a specific pain generator.

In order to understand why we have problems identifying a significant source of pain, I am suggesting that we explore and understand central sensitization – the phenomenon of increased sensitivity of the central nervous system to all stimuli because of tissue damage somewhere in the periphery. This means that an injury at a peripheral site – for example, the hip or shoulder – can cause sensitivity in the central nervous system, which controls how we perceive and respond to stimuli.  This causes too much response for the amount of input – which means someone who is sensitized will experience pain in response to a stimulus that normally would not cause pain.

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