A muscle relaxant is a drug that affects skeletal muscle function and decreases the muscle tone. It may be used to alleviate symptoms such as muscle spasms, pain, and hyperreflexia. The term “muscle relaxant” is used to refer to two major therapeutic groups: neuromuscular blockers and spasmolytics. Neuromuscular blockers act by interfering with transmission at the neuromuscular end plate and have no central nervous system (CNS) activity. They are often used during surgical procedures and in intensive care and emergency medicine to cause temporary paralysis. Spasmolytics, also known as “centrally acting” muscle relaxant, are used to alleviate musculoskeletal pain and spasms and to reduce spasticity in a variety of neurological conditions. While both neuromuscular blockers and spasmolytics are often grouped together as muscle relaxant, the term is commonly used to refer to spasmolytics only.
Tense, spasming muscles are often the underlying cause of back and neck pain. If the pain is severe or chronic and does not respond to over-the counter medications, muscle relaxants may be prescribed. Muscle relaxers:
- Reduce skeletal muscle spasms
- Relieve pain
- Increase mobility of the affected muscles
Muscle relaxers are used in addition to rest, physical therapy, and other measures to relieve discomfort. They are typically prescribed for short-term use to treat acute, painful musculoskeletal conditions. Muscle relaxers are occasionally prescribed for chronic pain (pain lasting longer than 3 months).
Muscle relaxers are not a class of drugs—meaning they do not all have the same chemical structure or work the same way in the brain. Rather, the term muscle relaxer is used to describe a group of drugs that act as central nervous system depressants and have sedative and musculoskeletal relaxant properties.
Muscle relaxers may be prescribed to treat back pain:
- Early in the course of back pain, on a short-term basis, to relieve pain associated with muscle spasms
- When back pain causes insomnia (for their sedative effect)
Muscle relaxers are also prescribed for other conditions such as fibromyalgia, multiple sclerosis, and seizure disorders.There are several types of muscle relaxer medications commonly used to treat back pain.
Common Muscle Relaxants
Muscle relaxers are usually prescribed to treat back pain in conjunction with rest and physical therapy. Common muscle relaxants include:
- Baclofen. Muscle tightness and muscle spasms, including those related to spine injuries, may be eased with baclofen. The medication may be helpful in treating multiple sclerosis and stabbing nerve pain. It is available as a tablet and can be taken by children as young as 12 years old. Some common side effects could include nausea and vomiting, confusion, drowsiness, headache, or muscle weakness. Baclofen is rated C in the FDA’s A through X pregnancy safety ranking for medications, with A being the safest. The C category means that the medication should only be used if the benefits outweigh the risks.
- Benzodiazepines. In addition to treating anxiety, alcohol withdrawal, and seizure disorders, such as epilepsy, benzodiazepines can also treat muscle spasms and skeletal pain. Benzodiazepines, such as diazepam (Valium), lorazepam (Ativan), and temazepam (Restoril), are typically only intended for short-term use. This limitation is due to their habit-forming potential and because they alter sleep cycles, leading to sleep difficulties once the drug is stopped. Benzodiazepines are sold as tablets, liquid, injections, and rectal gels. People who have myasthenia gravis, severe liver disease, serious breathing troubles, or some forms of glaucoma, should avoid taking diazepam. All benzodiazepines are rated D by the FDA for safety during pregnancy and are not recommended for women who are pregnant.
- Carisoprodol (Soma). Carisoprodol relaxes muscles and eases pain and stiffness caused by acute bone and muscle problems, often caused by an injury. It is taken by mouth in tablet form and is also available in combination with aspirin or aspirin and codeine. Carisoprodol can be habit-forming, particularly if used in conjunction with alcohol or other drugs that have a sedative effect, including opioids (such as codeine). Common side effects include drowsiness, dizziness, and headache. People with a history of blood disorders, kidney or liver disease, and seizures may need to avoid Carisoprodol. It is rated C in the FDA’s pregnancy safety ranking for medications.
- Chlorzoxazone (Lorzone). Chlorzoxazone is used for the relief of discomfort from acute, painful, musculoskeletal conditions. Chlorzoxazone is available as a tablet. Common side effects include drowsiness, dizziness, and nausea. Chlorzoxazone is not recommended for people with liver disease. It has not been rated by the FDA for safety during pregnancy.
- Cyclobenzaprine (Amrix, Fexmid, FlexePax Kit, FusePaq Tabradol). Cyclobenzaprine eases stiffness and pain from muscle cramps, also called muscle spasms. It is available as a tablet and extended-release capsule. Cyclobenzaprine itself is not intended for long-term use (more than 2 to 3 weeks). Common side effects include blurred vision, dizziness or drowsiness, and dry mouth. It is not advised for those with an overactive thyroid, heart problems, or liver disease. Cyclobenzaprine is rated B by the FDA for safety during pregnancy, making it the safest muscle relaxant to use while pregnant.
- Dantrolene (Dantrium). Dantrolene helps control chronic spasticity related to spinal injuries. It is also used for conditions such as stroke, multiple sclerosis, and cerebral palsy. Dantrolene is taken as a capsule or intravenous powder for injection. Drowsiness and sensitivity to light are common side effects. It can cause severe liver problems, and should not be taken by people with active liver disease. The FDA has given dantrolene a C rating for safety in pregnancy.
- Metaxalone (Skelaxin, Metaxall, and Metaxall CP, Lorvatus PharmaPak). Metaxalone targets pain and muscle spasms from sprains, strains, and muscle injuries. It is available as a tablet or injection. Common side effects include drowsiness, dizziness, nausea, and vomiting. Metaxalone is generally not recommended for people with a known tendency to become anemic, and who have kidney or liver disease. Metaxalone may affect blood sugar tests for people with diabetes. The FDA has not rated metaxalone for safety during pregnancy.
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Methocarbamol (Robaxin, Robaxin-750). Methocarbamol eases acute muscle and bone pain. It can be taken as a tablet or by injection. Common side effects include dizziness, headache, nausea, flushing, and blurred vision. Methocarbamol is generally not recommended to people with renal disease or failure, or a history of allergic reaction to the medication. The FDA has given methocarbamol a C rating for safety during pregnancy.
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Orphenadrine. Orphenadrine is a medication used to relieve pain and stiffness caused by muscle injuries. It is available as an extended-release tablet. Common side effects include dry mouth, lightheadedness, difficult urination, heartburn, nausea and vomiting. It is generally not recommended to people with previous sensitivities to the ingredients, myasthenia gravis, those with glaucoma or certain types of ulcers. The FDA has given orphenadrine a C rating for safety during pregnancy.
- Tizanidine (Comfort Pac with Tizanidine, Zanaflex). Tizanidine is used to treat muscle spasms caused by spinal cord injuries and other conditions such as multiple sclerosis. Tizanidine is available in tablet and capsule form and absorbs differently depending on whether it is taken on an empty stomach or with food. Common side effects include dry mouth, dizziness, constipation and tiredness. It should not be used by people taking fluvoxamine or ciprofloxacin or those who have liver disease. Tizanidine is rated in the C category for safety during pregnancy.
Sometimes the first muscle relaxers a doctor prescribes does not work as well as expected. It may be necessary to try an alternative if the initial prescription is not effective. Many drugs interact with muscle relaxers and a person should keep their health care provider informed of all prescription and non-prescription medications he or she is taking.
There is very little research regarding which muscle relaxers are most effective, so the choice of which medication—or whether to use one at all—is based on factors such as a person’s reaction to the medication and personal preferences, potential for abuse, possible drug interactions, and adverse side effects.
Medication is just one part of pain relief. These medications are intended to be one element, usually on a short-term basis, of an overall recovery strategy that includes rest, stretching, physical therapy, and other exercise.
Side Effects Associated with Muscle Relaxers
Side effects of muscle relaxers include:
- Sleepiness or grogginess
- Fatigue
- Dry mouth
- Constipation
- Nausea
More serious side effects include:
- Light-headedness or fainting
- Blurred vision
- Confusion
- Urinary retention
Any serious side effects should be reported to a doctor immediately.
Risks Associated with Muscle Relaxers
Muscle relaxers are a group of drugs that have a sedative effect on the body. They work through the brain, rather than directly on the muscles. Muscle relaxants are generally used for a few days and up to 3 weeks, but are sometimes prescribed for chronic back pain or neck pain.
To minimize risk, the doctor should be informed of any history of seizures, liver disease, and any other medical conditions or concerns. Women should inform their doctors if they are pregnant, plan to become pregnant, or are breast-feeding.
- Sleepiness. Because muscle relaxers are total body relaxants, they typically induce grogginess or sleepiness. As a result, it is not safe to drive or make important decisions while taking muscle relaxers. Muscle relaxers are often suggested for evening use due to their sedative effect.
- Interactions with alcohol. Drinking alcohol can be especially dangerous when taking muscle relaxers. The sedative effect of the medication is intensified with alcohol use, and combining the two can be fatal.
- Allergic reactions. No medication should be taken if the person has had an allergic reaction to it in the past, even if the reaction seemed mild. Symptoms of an allergic reaction include swelling in the throat or extremities, trouble breathing, hives, and chest tightness.
- Potential for abuse. Muscle relaxers have a risk of misuse and abuse. Some muscle relaxers, such as cyclobenzaprine, can be habit-forming on their own. Others may be taken in conjunction with other drugs, such as opioids, to create a high, and are therefore more likely to be abused.
Tapering off. Stopping a muscle relaxer abruptly can be harmful. Instead, the doctor will prescribe a gradual reduction in dosage.
Muscle relaxers are widely prescribed for acute back pain, often in conjunction with an over-the-counter or prescription pain medication. They are generally prescribed for a short time to relieve pain in the lower back or neck caused by muscle spasms, also called muscle cramps.
If a medication seems to cause problems, it is important to notify the doctor. Each medication works a little differently, and the doctor may be able to prescribe another that fits the individual’s needs better.