How do muscle relaxers work? Everything to know about muscle relaxers

Muscle relaxers are also known as muscle relaxants. They are a type of medication that doctors may prescribe to relieve muscle pain, muscle tension, or muscle spasms. They are often used to help with issues like lower back pain and conditions that affect the brain and spinal cord, like multiple sclerosis (MS).  

Each type of muscle relaxer works in a slightly different way. Some of these medications change activity in the central nervous system — which includes the brain and spinal cord — to help relieve muscle pain, stiffness, or spasms. Other muscle relaxers work by directly targeting your muscles.

Why might you take muscle relaxers?

Muscle relaxers are typically used for two purposes:

• To reduce muscle spasticity: Muscle spasticity is where you experience continuous muscle stiffness or tightness, which can interfere with movement and cause pain or discomfort. Spasticity is often caused by an injury to your brain or spinal cord. Conditions like MS and cerebral palsy can also cause muscle spasticity.
• To reduce muscle spasms or cramps: These are sudden, uncontrollable contractions of one or more muscles. They are often caused by muscle injury or strain. Issues like fibromyalgia and lower back pain can cause muscle spasms.

Doctors prescribe some muscle relaxers to help with both muscle spasms and spasticity.

Types of muscle relaxers

The main types of muscle relaxers include the following:

• Antispastics such as baclofen (Lioresal) and dantrolene (Dantrium). These help with muscle spasticity.
• Antispasmodics (non-benzodiazepines) like carisoprodol (Soma), cyclobenzaprine (Fexmid, Flexeril, Amrix), metaxalone (Skelaxin, Metaxall), methocarbamol (Robaxin), and tizanidine (Zanaflex). These medications may help with muscle spasms and have a sedative, or calming and relaxing, effect.
• Antispasmodics (benzodiazepines) like diazepam (Valium). These drugs can have a sedative effect, but they can also help reduce anxiety, improve sleep patterns, and help manage seizures.

Other drugs may also be used to help with muscle pain, spasms, or tension, even though these medications are not usually classified as muscle relaxers. For example, eszopiclone (Lunesta) is a sedative medication used to treat insomnia. It can have a calming effect on your body and mind, so it might help ease muscle pain or tension.

Pain-relief medications like ibuprofen (Advil) may sometimes be used to help with muscle pain and tension.

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How do muscle relaxers work?

Each type of muscle relaxer will work slightly differently. Some muscle relaxers work centrally on your brain and spinal cord (the central nervous system), while others target your muscles directly. For example:  

• Baclofen is a type of medication called a GABA agonist, which means it works by changing the way nerves transmit signals in your brain and spinal cord. By changing these signals, it can reduce muscle activity and improve tension and tone in your muscles.
• Dantrolene works by directly targeting your muscles. This drug prevents some of your muscle cells from releasing calcium ions, which are messengers that give your muscles the power to move. By reducing the release of calcium ions, dantrolene stops your muscles from contracting too much and allows your muscles to relax.
• Carisoprodol is a drug that reduces activity in your brain and spinal cord. This reduced activity can cause relaxation of your muscles. Some research suggests that this medication affects GABA receptors in your brain and spinal cord. GABA is a chemical that reduces nerve activity. By improving the action of GABA receptors, it can reduce your feelings of pain.
• Chlorzoxazone acts centrally on your central nervous system and interferes with nerve signals.

How do they make you feel?

Each type of muscle relaxer may make you feel slightly different. These medications will also affect each person differently. In general, muscle relaxers should lead to relaxation of your muscles and ease tension, pain, and spasms in your muscles.

In addition, muscle relaxers often have a sedative effect, so they may make you feel calmer and more relaxed but also drowsier and sleepier. Some of these medications may also cause you to experience some unpleasant side effects.

Possible side effects

The most common side effects of muscle relaxers are nausea and drowsiness. Other side effects include:

• For antispastics: Baclofen (Lioresal) may cause dizziness, weakness, tiredness, headaches, sleep issues, and constipation. Dantrolene (Dantrium) may also cause weakness, fatigue, dizziness, and, in some rare cases, injury to the liver.
• Antispasmodics (non-benzodiazepines): Antispasmodics like carisoprodol (Soma), cyclobenzaprine (Fexmid, Flexeril, Amrix), and methocarbamol (Robaxin) may also cause side effects like dizziness, fatigue, dry mouth, and headaches.
• Antispasmodics (benzodiazepines): Diazepam (Valium) may cause side effects like fatigue, confusion, low mood, irritability, headaches, constipation, changes in sex drive, and rashes.

Muscle relaxers also carry a risk of dependence and misuse. This means that if you take them too often or for too long, you may feel that you need these medications to function normally. You can reduce the risk of dependence by only taking the medications as advised by a doctor and by regularly reviewing your treatment plan.

Some muscle relaxers are not suitable for use at certain times during your life (for example, during pregnancy).

You may experience increased side effects when mixing muscle relaxers with alcohol, pain medications, or sleep aids. For this reason, you should speak with a doctor about your lifestyle and circumstances before starting and regularly while taking these medications.

Summary

Muscle relaxers work by easing muscle tension, pain, and spasms. There are two main types of muscle relaxers: antispastics and antispasmodics. Some of these medications work by suppressing activity in your brain and spinal cord. Other muscle relaxers work by targeting your muscles directly.

Muscle relaxers can make you feel calmer and more relaxed. However, these medications can also cause drowsiness and nausea. As muscle relaxers carry a risk of dependence and misuse, it is best to take these medications under the careful supervision of a doctor.