Muscle relaxants are medications that help reduce muscle spasms, which are involuntary muscle contractions caused by a spine-related problem, such as whiplash, fibromyalgia, or low back strain.
Often, muscle spasms cause severe pain and may limit your mobility.
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When are muscle relaxants prescribed?
Muscle relaxants are used to relieve muscle spasms which may result from some conditions which affect the nervous system, such as:
- Multiple sclerosis.
- Motor neurone disease.
- Cerebral palsy.
- Long-term injuries to the head or back.
Cannabis extract is usually started by a consultant in a hospital. It is normally prescribed for people with multiple sclerosis who have tried other muscle relaxants which are not working. In most cases it is given as a four-week trial to see if it helps with symptoms.
In addition, diazepam may be used to relieve lower back pain, or neck pain in conditions such as whiplash. It is addictive so cannot be used for more than a week or two. Methocarbamol is also used for muscle spasm in people with low back pain. Much of the pain in these conditions is due to muscle spasm. The cause of the spasm is different to the nervous system conditions above.
How should muscle relaxants be taken?
These medicines are usually taken by mouth (tablets, capsules or liquids). In general, your doctor will start off with a low dose and increase this gradually over a number of weeks. This is in order to help your body get used to these medicines. Injections into the back are always started in the hospital.
Cannabis extract is a spray for the mouth. It should be sprayed under the tongue or on to the inside of the cheek once or twice a day. Always change the area in your mouth where you spray, to prevent irritation of the mouth. Like other muscle relaxants you will normally start off with a low dose. The number of sprays used is normally increased over a number of days.
What are the possible side-effects?
As with most medicines, muscle relaxants have a number of possible side-effects. However, not everyone experiences them and they usually improve as your body adjusts to the new medicine. Most muscle relaxants cause muscle weakness as a side-effect. It is not possible in this leaflet to list all the possible side-effects for these medicines. However, see below for a list of the most common side-effects. For more detailed information, see the leaflet that comes with the medicine packet.
- Baclofen – feeling sick, tiredness, drowsiness, problems with eyesight, weakness, dizziness, light-headedness, headache, dry mouth, breathing difficulties, aching muscles, sleeplessness or nightmares, feeling anxious or agitated, confusion, unsteadiness, increased need to pass urine, shakiness, increased sweating, and skin rash.
- Dantrolene – feeling dizzy, sleepy, tired, or generally unwell, diarrhoea, feeling or being sick, tummy (abdominal) pain, headache, loss of appetite, rash, speech or sight difficulties, high temperature (fever), chills, difficulty in breathing, seizures. It may also cause inflammation of the lining around the heart (sometimes with fluid in the lungs). Liver toxicity is also a possible side-effect of dantrolene.
- Diazepam – feeling sleepy, weak, or light-headed, forgetfulness, feeling confused or unsteady, feeling (or being) aggressive.
- Methocarbamol – forgetfulness, allergic reactions, being anxious, blurred vision, a slow heart rate, being confused or dizzy, headache, heartburn, feeling or being sick, itching, rash, and low blood pressure.
- Cannabis extract – feeling dizzy, depressed mood, diarrhoea or constipation, mouth ulcers or pain, feeling tired or sick, appetite changes. Hallucinations have also been reported.

Who cannot take muscle relaxants?
For a full list of people who should not take each type of muscle relaxant, refer to the specific leaflet for that medication.
- Baclofen should not usually be given to people who have a stomach ulcer, epilepsy, mental health problems or diabetes.
- Dantrolene should not be given to people with liver, heart or breathing problems.
- Diazepam should be avoided in people who have severe breathing difficulties – for example, people who have myasthenia gravis and people with lung problems.
- Tizanidine should not usually be given to elderly people, or people who have severe problems with their liver.
- Methocarbamol should not be used for people who have myasthenia gravis or severe breathing problems. It also should not be used in people with epilepsy or brain damage.
- Cannabis extract can only be prescribed by specialists for people with multiple sclerosis. People who have a personal or family history of hallucinations or delusions or any other severe psychiatric disorder should not take cannabis extract.
Other considerations
Muscle relaxants are sometimes used to treat other conditions – for example, diazepam is sometimes used to treat anxiety or difficulty with sleeping (insomnia). It is given as a pre-medication (often called a ‘pre-med’) before an operation, particularly during procedures that may cause anxiety or discomfort.
It can also be used to treat seizures. Rectal diazepam tubes may be prescribed for this, as they are useful if a quick effect is needed or if it is not possible to give the medicine by mouth.
Some medicines that are given by injection into the vein during surgery are also known as muscle relaxants. They are sometimes called ‘neuromuscular blocking drugs’ and are used to relax the muscles during surgery. They work in a completely different way to baclofen, dantrolene, diazepam, tizanidine, and cannabis extract and are not discussed here.
There are a number of other things to consider when taking muscle relaxants:
- These medicines can cause drowsiness. If you feel drowsy when taking these medicines, do not operate machinery, do not drive, and do not drink alcohol.
- Baclofen should not be stopped suddenly. The dose should be lowered slowly over a few weeks and then stopped.
- Diazepam – people who take this medicine continuously for more than two weeks can become dependent on it. This means that withdrawal symptoms occur if the tablets are stopped suddenly.
Your doctor may prescribe a muscle relaxant to ease muscle spasms, reduce pain, and help your muscles move better. When your muscles move better, it makes other spine pain treatments, such as physical therapy, stretching, and exercise, more effective.
Understanding Spasticity Versus Spasm
Muscle relaxants treat 2 conditions: spasticity and spasm. Spasticity is marked by long-term muscle contraction caused by a brain or spinal cord injury. Spasms, on the other hand, are localized and occur because of a musculoskeletal issue.
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- Antispastics are prescribed to treat spasticity caused by neurological disorders, such as cerebral palsy or spinal cord injury.
- Antispasmodics are used to treat occasional muscle spasms.
While some antispasmodics may treat spasticity in addition to spasms, antispastics should not be used to treat spasms.
Muscle Relaxants for Muscle Spasms
Muscle spasms are painful and may restrict mobility, which can limit your ability to perform even basic activities. Painful, tight muscles can also interfere with getting a good night’s sleep.
Muscle relaxants may help reduce pain, and improve movement and range of motion, but your doctor will likely recommend that you first try acetaminophen or a nonsteroidal anti-inflammatory drug (NSAID). In some cases, these over-the-counter medications will be enough to help alleviate your pain.
If your muscle pain persists, your doctor may prescribe a muscle relaxant in addition to your pain medication. Below are common muscle relaxants (the generic names are listed first, with a brand name example in parentheses):
- Baclofen (Lioresal)
- Carisoprodol (Soma)
- Cyclobenzaprine (Amrix)
- Metaxalone (Skelaxin)
- Methocarbamol (Robaxin)
Special Considerations and Potential Muscle Relaxant Side Effects
Muscle relaxants for acute back or neck pain are usually prescribed to relieve short-term muscle pain—and some can be habit-forming. For these reasons, most doctors will write prescriptions with less than 2 weeks’ worth of medication. To reduce your risk of dependency or abuse, use your medication exactly as your doctor prescribes.
The most common side effects associated with muscle relaxants are drowsiness and dizziness. This is because muscle relaxants depress your central nervous system, making you less alert and attentive. As such, avoid alcohol and don’t perform tasks that require your complete attention, such as operating machinery or driving, while taking a muscle relaxant.
Muscle relaxants pose health risks when they are taken with certain medications and supplements, including opioids, sleep aid medications, and St. John’s wort. Make sure your doctor knows every medication and supplement you are taking before starting muscle relaxant therapy.
Muscle Relaxants: Part of a Multidisciplinary Treatment Plan
If your muscle pain doesn’t respond to over-the-counter medications, then muscle relaxants may be a good treatment option to alleviate your muscle spasms. For best results, muscle relaxants should be viewed as part of a treatment plan that may include gentle stretching, physical therapy, and exercise—not the sole treatment. As always, don’t hesitate to discuss your medications and comprehensive spine health plan with your doctor. A solid understanding of your therapeutic options is a strong defense against back pain.