Fibromyalgia Causes And Treatment With Guaifenesin, Amitriptyline, Kratom, Flexeril, And Others.

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Fibromyalgia (FM) is a disorder affecting approximately 2% of the world’s population. FM is characterized by musculoskeletal pain occurring throughout the body. Patients with this condition may also suffer from:


  • Fatigue
  • Mood problems
  • Memory issues
  • Sleep disturbances
  • Headaches
  • Anxiety
  • Depression


FM is a chronic disorder with subjective symptoms making diagnosis difficult. At present, FM cannot be diagnosed based on objective data.


Fibromyalgia has previously been thought of as a diagnosis to use when symptoms did not fit any other condition. Some physicians are still unsure whether this is an actual disorder. Patients may become depressed or frustrated due to a lack of compassion from various caregivers. 

Previously, many physicians believed patients were using fibromyalgia as an excuse to obtain pain medication. We are now finding that changing one’s lifestyle may be more effective than drugs. 

Suspected Causes of Fibromyalgia

The exact cause of fibromyalgia remains a mystery. It is most likely due to several factors. We believe some of these include:

  • Genetics: Fibromyalgia is more prevalent in people who have genetic relatives with the disorder. This leads us to think it may be due, at least partially, to a genetic mutation.
  • Trauma: This may be emotional or physical. We know that in some cases, fibromyalgia occurs after the person sustains an injury or experiences emotional stress. Victims of child abuse have a higher incidence as do those with posttraumatic stress disorder (PTSD). The brain may react differently to stress and pain in these individuals which may explain this link.
  • Mood disorders: Individuals with any mood disorder, including anxiety and depression, are more likely to suffer from fibromyalgia. 
  • Gender: Women are three times more likely to be diagnosed with fibromyalgia compared to men. 1This may be due to a difference in how women react to pain or society’s expectations of how women should respond to pain.
  • Sedentary lifestyle: People who don’t exercise are much more likely to suffer from fibromyalgia. Exercise is one of the main treatments.

There is some thought that FM may be the result of the body overreacting to pain signals. This could be due to an imbalance of neurotransmitters in the brain.

 Even weak signals may be perceived as pain if this is true.

The main obstacle in determining fibromyalgia’s cause is the fact that most people with this disorder also suffer from other conditions. 

Many have rheumatoid or osteoarthritis, migraine headaches, various mood disorders, and other maladies that cause pain. It is challenging to separate FM from these coexisting conditions.

A large number of the studies conducted on this subject have a small sample size, or patients are lost to follow up. More well-designed studies are needed to determine the causes of this debilitating condition.

Cymbalta for Fibromyalgia

A meta-analysis was performed using data from the year 2000 until March of 2019.  The purpose of this analysis was to determine efficacy and proper dosage of Cymbalta (duloxetine) in the treatment of fibromyalgia. This included seven studies with 2642 fibromyalgia patients. The results showed duloxetine was more efficacious than a placebo for pain control in these patients. 

The standard mean difference between duloxetine and placebo was -0.26 or 26% better pain relief. 

There were more adverse effects suffered by the duloxetine group, and withdrawal effects were more significant in those receiving 120 mg/day. The study concluded duloxetine was a great choice for relief of pain in fibromyalgia patients


A study published in June of 2019 compared duloxetine (Cymbalta) with pregabalin (Lyrica) in the treatment of fibromyalgia. 

All subjects were women with FM between 18-65 years of age. They were each assigned either duloxetine 30-60mg daily or pregabalin 75-150 mg daily for four weeks. 

The Widespread Pain Index (WPI) was used to measure pain severity. This scale quantifies body pain by asking patients if they have pain or tenderness in 19 body regions. The higher the score, the more widespread the pain. Duloxetine was significantly better in improving the WPI score with a mean difference of (-2.32) when compared with pregabalin.

The prevalence of nausea and the dropout rate was significantly higher in the Duloxetine group as compared to the pregabalin group.


A Cochrane database review was published in 2018 titled “Serotonin and noradrenalin reuptake inhibitors (SNRIs) for fibromyalgia.” This was a comprehensive study focusing on the efficacy of SNRI’s on numerous FM symptoms.

This study concluded that only a minority of patients might benefit from treatment with duloxetine or milnacipran. Most patients will not gain relief from FM symptoms, or they will experience adverse effects leading to drug discontinuation. 

There is no evidence to support the use of other SNRIs such as venlafaxine or desvenlafaxine in the treatment of FM.


Lyrica and Neurontin for Fibromyalgia

There was a Cochrane review published on the effects of anticonvulsants on FM. Since the lead author received financial support from commercial sponsors, this review has been withdrawn from publication.  


This study was, however, listed as a reference in the European League Against Rheumatism (EULAR) revised recommendations for the management of fibromyalgia. 


Pregabalin is listed as a pharmacotherapy for severe pain and severe sleep problems. Neurontin (gabapentin) is not recommended in the treatment of FM, according to EULAR.


Amitriptyline for Fibromyalgia

There is evidence that amitriptyline can help with sleep, fatigue and pain in FM at low doses. Five reviews involving 919 subjects found those receiving amitriptyline were 60% more likely to acheive a 30% reduction in pain. A moderate improvement in sleep and a small effect on fatigue were also shown.


Guaifenesin and fibromyalgia

Guaifenesin is an expectorant used primarily to loosen mucous in the airways. This helps the patient cough up the mucous and remove it from the body leading to more effective breathing. Guaifenesin is sold under the popular brand name Robitussin. It is also available under the brand name Mucinex as a 12-hour tablet formulation.


There is a protocol available on line that promotes the use of guaifenesin in the treatment of fibromyalgia. I do not see any harm in trying this method if you suffer from FM. Guaifenesin has few side effects. It is important to note that this protocol states that salicylates of any kind must be avoided for guaifenesin to be effective. This includes aspirin and all topical salicylate formulations. The protocol can be found at the link listed below:


A study conducted in May of 2009 used a telephone survey of 632 women to gain insight into the subjective pain relief obtained by several agents in the treatment of FM. 


Of the women surveyed, 434 claimed to have FM while 198 denied having the condition. The women had an age range of 18-80 years. 


The results of this study showed that half of the FM group were taking antidepressant medication. Tri-cyclic antidepressants (TCA’s) had strong effectiveness while serotonin reuptake inhibitors (SSRIs) had only moderate effectiveness in treating FM. Few were taking SNRI’s at this time. 


Almost 30% of the FM sample were taking non-steroidal anti-inflammatory drugs (NSAIDS). 


I included this study because even though it was conducted in 2009, it showed that the most effective medications to treat FM according to the subjective reports of the patients were opiate narcotics and guaifenesin. The narcotics aren’t surprising, but guaifenesin is.


Kratom for Fibromyalgia

Kratom is a substance obtained from a tropical evergreen tree found in Southeast Asia. This substance has been used for centuries to improve stamina and increase the energy of workers in its native region.

Kratom is available as a supplement in the US. People utilize it to treat diarrhea, pain, and to decrease the symptoms of opiate withdrawal.

An anonymous national survey was conducted in 2016 in an attempt to discover the usage patterns of Kratom in the US. This survey included 8049 Kratom users.

It is known that Kratom is used as an alternative to opiates. Fibromyalgia had the lowest proportion of “significant improvement” responses in this survey. This is expected as opioids are not recommended as a treatment for FM


Flexeril for Fibromyalgia

Cyclobenzaprine (Flexeril) is a muscle relaxant used for various musculoskeletal disorders.  

A systemic review of 312 patients taking cyclobenzaprine for FM found 85% suffered side effects and only 71% of the subjects were able to complete the studies.  

This review concluded sleep was slightly improved, but pain was not.  

Cyclobenzaprine can be used for severe sleep problems in FM


Trazodone is an antidepressant used mostly for insomnia at the current time.  This medication was not mentioned in the EULAR revised recommendations for the management of fibromyalgia.  

If other sleep agents recommended fail, I would not be opposed to trialing trazodone. This drug is effective for sleep at low doses.  Getting the proper amount of sleep is very important.

Celexa and Fibromyalgia

Citalopram belongs to a class of drugs known as selective serotonin reuptake inhibitors (SSRIs). Seven systematic reviews were conducted looking at this drug class for the treatment of fibromyalgia. These medications may have a small effect on pain and fatigue but do not help with sleep. Since SNRI’s discussed above are more useful for FM, SSRIs are not recommended.

The EULAR revised recommendations for the management of fibromyalgia were published in 2017


Michael Brown pictured with Final Thought written

The EULAR recommendations for the treatment of fibromyalgia maintain that prompt diagnosis and patient education are critical. The patient should be assessed for pain, level of function, and management should be geared towards improving the quality of life.

Non-pharmacological treatments should be initiated first. These include physical therapy with an emphasis on individualized exercise. Other therapies, such as acupuncture and hydrotherapy, may also be tried at this stage.

Psychological therapies should mainly consist of cognitive-behavioral therapy. If depression and anxiety are severe, psycho-pharmacological treatment can be utilized.

Recommendations for pharmacotherapy, according to EULAR, are as follows:

Drugs that should not be used:

  • Strong opioids
  • Sodium oxybate
  • Corticosteroids
  • Growth hormone

Drugs recommended for severe pain:

  • Duloxetine
  • Pregabalin
  • Tramadol

Drugs recommended for severe sleep problems:

  • Low dose amitriptyline
  • Cyclobenzaprine
  • Pregabalin

I have attempted to review the most up to date medication treatments for fibromyalgia in this post. I have included the recommendations from EULAR as well as information on Kratom, guaifenesin, and trazodone.

I do not recommend the use of Kratom at this time. I believe guaifenesin may have a benefit, and it has very few side effects. Trazodone is a good drug for insomnia at low doses, so it may be tried if other treatments fail.

After researching this subject, it seems that exercise, hypnosis, guided imagery, and other non-pharmacological treatments are the preferred treatment of fibromyalgia.

More research will surely be done on this subject, and hopefully we will obtain better treatments in the future.   

Thank you for reading my blog, and please contact me with questions.

Michael Brown in Lab Coat with arms crossed

Michael J. Brown, RPh, BCPS, BCPP

Mr. Brown is a Clinical Pharmacist specializing in pharmacotherapy and psychiatry.

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