Muscle Relaxants for Fibromyalgia

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Skeletal muscle relaxants are a broad group of medications that are approved by the US Food and Drug Administration (FDA) to treat muscle spasticity caused by neurological disorders or to treat acute musculoskeletal pain conditions. They are classified into one of two types: antispasticity or antispasmodic agents.

Those in the antispasticity group are used to reduce spasticity that interferes with overall functioning or activities of daily living. Conditions marked by spasticity can best be described as those that cause exaggerated jerking, exaggerated reflexes, twisting and repetitive motions, twitching, paralysis, lack of dexterity, and fatigability. These include cerebral palsy, multiple sclerosis, traumatic brain injury, or individuals who have sustained injury to their spinal cord. The only skeletal muscle relaxant drugs that are approved to treat spasticity are baclofen (Lioresal®), dantrolene (Dantrium®), and tizanidine (Zanaflex®

Medications in the antispasmodic group are typically prescribed as supplemental therapy for individuals who experience acute, painful musculoskeletal problems, such as fibromyalgia, tension headaches, myofascial pain syndrome, and lower back or neck pain.) Common examples of antispasmodic drugs include carisoprodol (Soma®), chlorzoxazone (Parafon Forte DSC®), cyclobenzaprine (Flexeril®), metaxalone (Skelaxin®), methocarbamol (Robaxin®), and orphenadrine (Norflex®).

Each muscle relaxant works in a specific way to relieve spasticity or muscle spasms and pain. Baclofen and tizanidine work by inhibiting the transmission of various chemicals involved in the processing of nerve signals, whereas the manner in which carisoprodol, chlorzoxazone, cyclobenzaprine, metaxalone, methocarbamol, and orphenadrine work to improve muscle spasms is not entirely understood, but many researchers believe it is somehow related to sedation.

Muscle Relaxants for Fibromyalgia

Recently published review articles have referenced the importance of including muscle relaxants as part of the multidisciplinary treatment of fibromyalgia (Han et al., 2011; Dussias et al., 2010). However, despite their common appearance in the therapeutic regimens of many fibromyalgia patients, there is a lack of research directly related to the specific use of muscle relaxants for fibromyalgia symptoms.

A 2004 meta-analysis evaluated the findings from five, randomized, placebo-controlled trials (the “gold standard” for research study design) to determine the effectiveness of cyclobenzaprine as treatment for fibromyalgia (Carette et al., 1994; Hamaty et al., 1989; Quimby et al., 1989; Reynolds et al., 1991; Bennett et al., 1988). A meta-analysis is a type of research study that integrates and analyzes data from a number of independent research studies. In this particular study, data from 312 fibromyalgia patients (95% of whom were women with an average age of 46) were collectively analyzed to determine what impact, if any, fibromyalgia had on sleep, fatigue, pain, and tender points. Following the meta-analysis, the researchers found that patients treated with cyclobenzaprine were more likely to identify themselves as “improved” versus those who were treated with placebo. In addition, a significant improvement in sleep was found for a number of patients. The analysis did not, however, reveal that cyclobenzaprine treatment was related to any improvements in tender points or fatigue (Tofferi et al., 2004).

A 1989 study be Vaeroy et al. studied 43 female patients with fibromyalgia over an eight week course of therapy with either a combination of carisoprodol, acetaminophen, and caffeine (20 patients), or placebo (23 patients). Nearly half of those in the placebo group used additional pain medications throughout the duration of the study, versus only 20% of those in the treatment group. Furthermore, the study found that those in the active treatment group experienced significant improvements in pain, sleep quality, and general well-being. The researchers concluded that the combination therapy of carisoprodol, acetaminophen, and caffeine are effective at treating various fibromyalgia-related symptoms (Vaeroy et al., 1989). The findings of this study should be interpreted with caution, however, due to the small sample size.

 

The following information provides a brief overview of the major skeletal muscle relaxants.

Baclofen

Baclofen (Lioresal®) exerts its effects on the spinal cord and blocks the transmission of nerve signals between muscular nerves. It is one of only three muscle relaxants approved by the FDA to treat spasticity. It is commonly used by individuals with multiple sclerosis or diseases of the spinal cord, however it can also be used to relieve pain and improve muscle function. Baclofen is available in tablet form and is usually taken three times per day. The full effects of baclofen are not typically observed until a few weeks following the initiation of treatment. Individuals who have a history of kidney disease, epilepsy, ulcers, stroke, rheumatic diseases, cerebral palsy, Parkinson’s disease or any psychological diseases should talk to their doctor before pursuing therapy with baclofen. Baclofen may cause side effects such as drowsiness, dizziness, weakness, confusion, or upset stomach. Patients who experience difficulty breathing or seizures should contact their treating physician immediately, as these are signs of a severe adverse reaction to the drug.

Dantrolene

Dantrolene (Dantrium®) is the second of the three FDA-approved medications used to treat spasticity. It is commonly used for spinal cord injuries, stroke, multiple sclerosis, cerebral palsy, and other conditions. It works to relieve spasticity by decreasing the release of calcium from skeletal muscle cells, a process which is essential for muscle contraction. It is available in capsule form and is initially given one per day, with dosing gradually increased to two to four times per day. Dantrolene may interact negatively with diazepam (Valium®), certain sedative medications, sleeping pills, tranquilizers, and vitamins. It can also interfere with estrogen supplements, as well as certain medications used to treat seizures, allergies, and colds. Therefore, any individuals who are taking these medications should inform their doctor prior to starting therapy with dantrolene. Individuals with heart, lung, or rheumatic disease should use dantrolene with caution. Furthermore, those with pre-existing liver disease should not use dantrolene, as it has the potential to cause severe liver damage. Dantrolene also increases susceptibility to sunlight, therefore individuals who take this medication should avoid prolonged and/or unprotected exposure to sunlight. Side effects of dantrolene include muscle weakness, drowsiness, dizziness, diarrhea, fatigue, and difficulty swallowing. Seizures are a sign of a serious adverse reaction and should be reported to the treating physician immediately if they occur.

Tizanidine

Tizanidine is the last of three drugs approved by the FDA for the treatment of spasticity. It is frequently used to reduce muscle spasms and improve muscle tone in patients with multiple sclerosis, and may also be used in individuals suffering from the effects of stroke, traumatic brain injury, or spinal cord injury. Tizanidine works in a manner similar to baclofen, by slowing transmission of nerve signals between the brain and muscles. Tizanidine is available in both tablet and capsule forms, and is typically taken two or three times a day. The medication contained in the capsule form acts differently than the tablet form, therefore one product cannot be substituted for another. Dosing is usually started low and then gradually increased to an effective level. Individuals who are taking tizanidine should not stop their therapy abruptly; this may result in rapid heartbeat, increased blood pressure, or muscle tightness. Discontinuation of therapy with tizanidine should be done gradually. Tizanidine should not be used concurrently with the antibiotic ciprofloxacin (Cipro®) or the drug fluvoxamine (Luvox®), which is used to treat obsessive-compulsive disorder and generalized anxiety disorder. In addition, tizanidine has the potential to interact negatively with a great number of prescription and non-prescription medication, therefore it is important for individuals considering tizanidine therapy to mention any and all drugs (prescription and otherwise) that they are taking to avoid serious adverse interactions. Side effects of treatment with tizanidine include dizziness, drowsiness, weakness, nervousness, depression, vomiting, tingling in the upper or lower extremities, dry mouth, constipation, diarrhea, upset stomach or heartburn, increased muscle spasms, back pain, rash, and increased sweating. The following are a list of potentially severe side effects, which if experienced during treatment with tizanidine, should be reported to the treating physician immediately: nausea, extreme tiredness, unusual bleeding or bruising, decreased energy, loss of appetite, pain in the upper right section of the stomach, yellowing of the skin or eyes, flu-like symptoms, hallucinations, decreased heartbeat, and vision changes.

Carisoprodol, Chlorzoxazone, Metaxalone, and Methocarbamol

Carisoprodol (Soma®), chlorzoxazone (Parafon Forte DSC®), metaxalone (Skelaxin®), and methocarbamol (Robaxin®) are antispasmodic medications that are typically used along with rest, physical therapy, and other therapeutic modalities to relax muscles and relieve muscle pain due to strains, sprains, and other types of muscle injury. All four medications are available in tablet form and are generally taken three to four times per day. Methocarbamol may be increased to up to six times per day. All three medications can have negative drug interactions with certain sedative medications, sleeping pills, tranquilizers, and vitamins, and can also interfere with medications used to treat allergies and the common cold. Carisoprodol should always be taken with food or milk in order to avoid an upset stomach. Furthermore, individuals with a history of liver disease should not take chlorzoxazone, and those over age 65 should not take chlorzoxazone or methocarbamol, as they are typically not as safe or effective as other medications when used in older adults.

Common side effects associated with the use of these medications include drowsiness, dizziness, upset stomach, clumsiness, headache, increased heart rate, upset stomach, vomiting, and nervousness. Methocarbamol use may also result in blurred vision, fever, and discolored urine. Signs of serious adverse reactions to carisoprodol include difficulty breathing, fever, weakness, and a burning sensation in the eyes. Signs of a serious adverse reaction to chlorzoxazone include skin rash or itching, yellowing of the skin or eyes, and stomach pain. Adverse reaction to metaxalone is also characterized by severe rash, difficulty breathing, yellowing of the eyes or skin, unusual bleeding or bruising, unexplained tiredness or weakness, and seizures. Signs of a serious reaction to methocarbamol include rash and itching.

Cyclobenzaprine

Cyclobenzaprine (Flexeril®) is also used to relieve the pain and discomfort that results from muscle sprains, strains, and other injuries. It is available in two forms – a tablet and an extended-release capsule. The tablet is typically taken two to four times per day, whereas the extended-release capsule is generally taken once or twice daily. Cyclobenzaprine should not be taken for more than three weeks unless directed by a physician. Individuals considering therapy with cyclobenzaprine should be sure to tell their doctor about any medications they have taken in the prior two weeks, in particular medications prescribed for depression, seizures, allergies, coughs, colds, monoamine oxidase inhibitors (MAOIs) such as Nardil or Parnate, certain sedative medications, sleeping pills, tranquilizers, and vitamin supplements. Individuals with a history of overactive thyroid gland, heart disease, glaucoma, or difficulty urinating should use caution when taking cyclobenzaprine, as should individuals over the age of 65. Side effects commonly associated with the use of cyclobenzaprine include drowsiness, dry mouth, dizziness, and upset stomach.

Orphenadrine

Orphenadrine (Norflex®) is also useful at relieving the pain associated with muscle sprains, strains, and injuries. It is available in tablet form (conventional or extended-release) and is typically taken twice per day. As with the other muscle relaxants described above, orphenadrine has the potential for negative drug interactions therefore patients should provide a list of current and planned medications (prescription and non-prescription) when discussing therapy with their doctor. It is especially important to mention the following medications: amantadine (Symadine®), fluphenazine (Prolixin®), haloperidol (Haldol®), depression medications, perphenazine (Trilafon®), prochlorperazine (Compazine®), promethazine (Phenergan®), and trifluoperazine (Stelazine®). In addition, individuals who have a history of glaucoma, myasthenia gravis, ulcers, urinary tract or intestinal blockages, enlarged prostate, irregular heartbeat, or liver, kidney or heart disease should discuss their options carefully, as orphenadrine may or may not be the most appropriate therapy. Common side effects associated with the use of orphenadrine include dry mouth, drowsiness, dizziness, lightheadedness, upset stomach, vomiting, constipation, difficulty urinating, blurred vision, and headache. Serious side effects include fast or irregular heartbeat, fainting, confusion, hallucinations, and skin rash.

Important information Regarding Pregnancy and Alcohol Use

Women who are pregnant, may become pregnant, or who are breastfeeding should discuss their options with their physician to determine if a muscle relaxant is acceptable to use. Furthermore, most muscle relaxants have the potential to cause marked drowsiness, therefore it is advisable to refrain from driving a car or operating machinery until patients are aware of how their particular medication will affect them. Finally, the use of alcohol while taking certain muscle relaxants may contribute to increased drowsiness and make other side effects worse.

Learn more about treating fibromyalgia with anti-depressant medications HERE.

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References

1.        Dean, L. Comparing Muscle Relaxants.  National Center of Biotechnology Information (NCBI). h

2.        Chou R, Peterson K. Drug Class Review on Skeletal Muscle Relaxants. Oregon Evidence-based Practice Center. Oregon Health & Science University. Final Report, May 2005.    Accessed April 19, 2012.

3.        Baclofen Oral. MedlinePlus; National Institutes of Health.  Last reviewed 09/01/2010; Accessed 04/19/2012.

4.        Dantrolene Oral. MedlinePlus. National Institutes of Health.Last reviewed 09/01/2010; Accessed 04/19/12.

5.        Tizanidine. MedlinePlus. National Institutes of Health.   Last reviewed 02/11/2012; Accessed 04/19/2012.

6.        Carisoprodol. MedlinePlus. National Institutes of Health.   Last reviewed 08/01/2010; Accessed 04/19/2012.

7.        Chlorzoxazone. MedlinePlus. National Institutes of Health.   Last reviewed 07/01/2010; Accessed 04/19/2012.

8.        Cyclobenzaprine. MedlinePlus. National Institutes of Health.   Last reviewed 10/01/2010; Accessed 04/19/2012.

9.        Metaxalone.  MedlinePlus. National Institutes of Health.  Last reviewed 09/01/2010; Accessed 04/19/2012.

10.     Methocarbamol. MedlinePlus. National Institutes of Health.Last reviewed 10/01/2010; Accessed 04/19/2012.

11.     Orphenadrine. MedlinePlus. National Institutes of Health.   Last reviewed 12/01/2010; Accessed 04/19/2012.

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