Muscle Relaxers: Types, Uses, Side Effects and Safety Risks
Updated: 6 days ago
Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026 · How we review
Quick Answer: What are muscle relaxers?
Muscle relaxers are prescription medicines that affect skeletal muscle function and are used to treat muscle spasms, spasticity and musculoskeletal pain. The two main classes are antispasmodics, used mainly for back pain and spasms, and antispastics, used mainly for spasticity. Most cause drowsiness, and mixing them with alcohol or taking too much can be dangerous. [1]
What the research says
Short-term pain relief for acute low back pain is small. A meta-analysis of 31 trials with 6,505 adults found non-benzodiazepine antispasmodics lowered pain by about 7.7 points on a 0–100 scale within two weeks, a change the authors judged not clinically important, with no clear drop in disability and about a 60% higher risk of side effects (RR 1.6). (Cashin et al., BMJ, 2021) [2]
More pain relief than placebo, but more side effects. A 2025 review of 50 trials (7,531 people) found non-benzodiazepine muscle relaxers increased the likelihood of pain relief for acute low back pain versus placebo, while side effects were 56% more frequent (RR 1.56) and nervous-system side effects were 2.4 times as frequent (RR 2.40). (Manca et al., Eur Spine J, 2025) [3]
Use has grown fast, often alongside opioids. In the United States, office visits with a muscle relaxer prescription nearly doubled from 15.5 million in 2005 to 30.7 million in 2016, and an opioid was also recorded in 67.2% of visits where a muscle relaxer was being continued. (Soprano et al., JAMA Netw Open, 2020) [4]
Key takeaways
Muscle relaxers are prescription-only in the United States; there are no over-the-counter versions. [1]
Antispastics such as baclofen treat spasticity; antispasmodics such as cyclobenzaprine treat spasms and musculoskeletal pain. [1]
Antispasmodics are not a first choice for back pain; they are usually tried after other treatments have not worked. [1][7]
Drowsiness is the most expected side effect, so driving and important decisions need extra caution. [1]
Carisoprodol and diazepam are controlled substances with addiction potential. [1]
Never combine muscle relaxers with alcohol, and treat any overdose signs as an emergency. [1]
Muscle relaxers at a glance
Question | Short answer |
What are they? | Prescription medicines that affect skeletal muscle function [1] |
Main types | Antispasmodics and antispastics [1] |
Main uses | Muscle spasms, spasticity and musculoskeletal pain [1] |
Available over the counter? | No, not in the United States [1] |
Most common side effect | Drowsiness and fatigue [1] |
Controlled (addictive) types | Carisoprodol and diazepam [1] |
Biggest dangers | Alcohol interactions and overdose [1] |
Usual length of use | Short periods, because some types can cause addiction [1] |
What are the types of muscle relaxers?
Muscle relaxers fall into two major classes, antispasmodics and antispastics, which differ in what they treat, how they work and which side effects they cause. [1][6]
This guide covers skeletal muscle relaxers, the medicines that act on the muscles you use to move. They are different from smooth muscle relaxers, which act on muscles you do not control, such as those in the stomach, intestines and blood vessels. [1]
Class | Medicines (brand examples) | Main use |
Antispasmodics | Carisoprodol (Soma, Vanadom), chlorzoxazone (Lorzone, Parafon Forte DSC, Relax-DS, Remular S), cyclobenzaprine (Fexmid, Flexeril), metaxalone (Metaxall, Skelaxin), methocarbamol (Robaxin), orphenadrine (Norflex) | Muscle spasms and musculoskeletal pain, especially low back pain |
Antispastics | Baclofen (Lioresal), dantrolene (Dantrium) | Spasticity |
Both effects | Tizanidine (Zanaflex), diazepam (Valium) | Spasms and spasticity |
Table based on [1].
What conditions do muscle relaxers treat?
Muscle relaxers treat two main problems: antispastics treat spasticity, and antispasmodics treat muscle spasms and musculoskeletal pain. [1]
Antispastics for spasticity
Spasticity is a disruption in muscle movement that makes certain muscles contract all at once, either when you try to move or even at rest. It usually comes from damage to nerve pathways in the brain or spinal cord that control movement and stretch reflexes. [1]
Conditions that can cause spasticity include:
Multiple sclerosis (MS)
Brain or head injury
Baclofen is considered the first-line treatment for spasticity, especially in adults with spinal cord injuries. Do not stop baclofen suddenly, because withdrawal can cause hallucinations, seizures and high fever; your doctor will lower the dose slowly. [1]
Antispasmodics for spasms and pain
Antispasmodics are prescribed mainly for musculoskeletal and myofascial pain, especially low back pain, and for muscle spasms. [1]
They are not a first-line treatment. Doctors usually turn to them only after first- or second-line options have not worked, because of their side effects and, for some types, addiction potential. [1][7]
Low back pain is among the top five reasons people visit a primary care provider, and most cases get better without medical treatment. [1]
Some of these medicines also treat conditions unrelated to muscles. Diazepam, for example, is sometimes prescribed for anxiety and seizures. [1]
How do muscle relaxers work in the body?
Most muscle relaxers work as central nervous system depressants, which causes a sedative effect, or they stop nerves from sending pain signals to the brain. [1]
How are muscle relaxers taken?
Muscle relaxers come in several forms, including tablets, capsules, liquid solutions and injections, depending on the medicine. [1]
Your doctor or pharmacist will tell you exactly how and when to take yours. Follow those instructions closely. [1]
Are muscle relaxers available over the counter?
Muscle relaxers are not available over the counter in the United States; every type requires a prescription. [1]
For everyday muscle soreness, some over-the-counter medicines can help, such as NSAIDs (nonsteroidal anti-inflammatory drugs) and acetaminophen. [1]
How well do muscle relaxers work?
Antispastics are effective for spasticity, but high doses can cause unwanted side effects. Physical therapy and Botox injections can also help with spasticity. [1]
For muscle pain and spasms, the picture is less clear. There is little research showing whether antispasmodics work better than NSAIDs or acetaminophen, and antispasmodics cause more side effects than either. [1]
A large overview of Cochrane reviews found that no medicine studied gave a large or medium pain benefit for low back pain. For acute low back pain, both NSAIDs and muscle relaxers gave a small effect on pain, and muscle relaxers increased the risk of side effects. [5]
Antispasmodics | NSAIDs or acetaminophen | |
Role for back pain | Alternative after other treatments fail [1] | Common over-the-counter options for soreness [1] |
Proven better for muscle pain? | Research is lacking [1] | Research is lacking [1] |
Side effects | More side effects [1] | Fewer side effects [1] |
Prescription needed (US)? | Yes [1] | No [1] |
What are the side effects of muscle relaxers?
The most common side effects of muscle relaxers are drowsiness, fatigue, dizziness, nausea, headache and dry mouth. Each medicine has its own side effect profile, so ask your doctor or pharmacist about the one you take. [1]
Common side effects | More serious side effects |
Drowsiness and fatigue | Fainting |
Dizziness | Blurred vision |
Nausea | |
Headache | |
Dry mouth |
Table based on [1].
Talk to your doctor if any side effect bothers you. [1]
Do muscle relaxers make you sleepy?
Muscle relaxers can make you sleepy because of how they affect the central nervous system. Be careful with driving, operating heavy machinery or making important decisions while taking them. [1]
Are muscle relaxers addictive?
Carisoprodol and diazepam are controlled substances, meaning they can cause addiction and withdrawal symptoms if you become dependent and then stop. The other prescription muscle relaxers are not controlled substances. [1]
Avoid carisoprodol and diazepam if you or a family member has a history of substance use disorder. [1]
If you feel dependent on either medicine, or your dose no longer controls your symptoms, do not take more than prescribed. Talk to your doctor right away. [1]
Long-term use can build tolerance and physical dependence. [1]
Because of this addiction potential, doctors usually prescribe muscle relaxers only for short periods. [1]
Why is it dangerous to mix muscle relaxers with alcohol?
Mixing muscle relaxers with alcohol is dangerous because both are depressants that slow the central nervous system, so together their effects become much stronger. Do not drink alcohol while taking a prescription muscle relaxer. [1]
The combination can cause:
Extreme dizziness
Extreme drowsiness
Blurred vision
Low blood pressure
Fainting
Memory problems
Liver damage
A higher risk of overdose [1]
What are the signs of a muscle relaxer overdose?
Signs of a muscle relaxer overdose include changes in consciousness, hallucinations, seizures, slowed breathing (respiratory depression), cardiac arrest, coma and death. [1]
Overdose risk rises with misuse, especially of carisoprodol and diazepam. Because most muscle relaxers are sedatives, some people take them alone or with other drugs for nonmedical reasons to feel euphoria or detachment, which greatly increases this danger. [1]
If you or someone near you shows signs of an overdose, call your local emergency number or go to the nearest emergency room right away. [1]
When should you call a doctor about muscle relaxers?
You should call your doctor about a muscle relaxer if side effects bother you, your symptoms are not improving or are getting worse, or you think you are becoming dependent on it. [1]
Keep regular appointments while you take a muscle relaxer so your doctor can check how well it is working. [1]
Conclusion
Muscle relaxers can help with spasticity, muscle spasms and muscle-related pain, but they come with real trade-offs: drowsiness, possible dependence with some types, and serious risks when mixed with alcohol or taken in excess. Research shows the pain benefit for back pain is modest while side effects are common, so they work best as a short, supervised part of a wider plan. Talk openly with your doctor about every option for your symptoms so you can choose the safest treatment together. [1][2][3]
Want more clear, research-backed health guides? Explore our back pain guide and our guide to muscle spasms and cramps, and follow Rinnit on Instagram and YouTube for new articles every week.
FAQ
What are muscle relaxers?
Muscle relaxers are prescription medicines that affect skeletal muscle function. Doctors use them to treat muscle spasms, spasticity and musculoskeletal pain. [1]
What is the difference between antispasmodics and antispastics?
Antispasmodics are mainly used for muscle spasms and musculoskeletal pain such as low back pain, while antispastics are mainly used for spasticity. They also work in different ways and have different side effects. [1]
Can you buy muscle relaxers over the counter?
Muscle relaxers are not sold over the counter in the United States. NSAIDs and acetaminophen are over-the-counter options that can help with muscle soreness. [1]
Which muscle relaxer is used first for spasticity?
Baclofen is considered the first-line treatment for spasticity, especially for adults with spinal cord injuries. [1]
Are muscle relaxers addictive?
Carisoprodol and diazepam are controlled substances that can cause addiction and withdrawal symptoms. The other prescription muscle relaxers are not controlled substances. [1]
Can I drink alcohol while taking a muscle relaxer?
Drinking alcohol while taking a muscle relaxer is not safe. Both slow the central nervous system, and together they can cause extreme drowsiness, low blood pressure, fainting, liver damage and overdose. [1]
When should I go to the emergency room after taking a muscle relaxer?
Go to the emergency room or call emergency services if you notice overdose signs such as changes in consciousness, hallucinations, seizures or slowed breathing. [1]
How long does it take for a muscle relaxer to work?
Many muscle relaxers taken by mouth start to work within about an hour, but timing differs by medicine. Your pharmacist can tell you what to expect from yours.
Can you take muscle relaxers long term?
Antispasmodics for back pain are usually meant for short-term use, often a few days to a couple of weeks. Antispastics for conditions such as multiple sclerosis may be used longer under a doctor's care.
Are muscle relaxers safe for older adults?
Older adults are more likely to have drowsiness, confusion and falls with muscle relaxers. Doctors often avoid them or use lower doses, so talk with your doctor about safer options.
Related Reading
Antispasmodics: Understanding Smooth Muscle Relaxants explains how antispasmodic medicines ease muscle spasms and their side effects.
Muscle Spasms and Muscle Cramps: Causes, Treatment and Prevention covers why muscles cramp or spasm and how to get relief.
Benzodiazepines (Benzos): Uses, Side Effects and Risks explains how benzodiazepines work, their uses and dependence risks.
Baclofen Pump: How It Works, Who It Helps, Risks and Recovery describes an implanted pump that delivers baclofen for severe spasticity.
References
Cleveland Clinic. Muscle Relaxers: What They Are, Uses, Side Effects & Types. Cleveland Clinic. Last updated February 7, 2023. https://my.clevelandclinic.org/health/treatments/24686-muscle-relaxers
Cashin AG, Folly T, Bagg MK, et al. Efficacy, acceptability, and safety of muscle relaxants for adults with non-specific low back pain: systematic review and meta-analysis. BMJ. 2021;374:n1446. PMID 34233900. https://doi.org/10.1136/bmj.n1446
Manca A, Cugusi L, van Tulder M, et al. Oral non-benzodiazepine muscle-relaxants for people with acute and chronic primary low back pain: a systematic review with meta-analysis. Eur Spine J. 2025;34(6):2347-2366. PMID 40186696. https://doi.org/10.1007/s00586-025-08786-0
Soprano SE, Hennessy S, Bilker WB, et al. Assessment of Physician Prescribing of Muscle Relaxants in the United States, 2005-2016. JAMA Netw Open. 2020;3(6):e207664. PMID 32579193. https://doi.org/10.1001/jamanetworkopen.2020.7664
Cashin AG, Wand BM, O'Connell NE, et al. Pharmacological treatments for low back pain in adults: an overview of Cochrane Reviews. Cochrane Database Syst Rev. 2023;4(4):CD013815. PMID 37014979. https://doi.org/10.1002/14651858.CD013815.pub2
Chang WJ. Muscle Relaxants for Acute and Chronic Pain. Phys Med Rehabil Clin N Am. 2020;31(2):245-254. PMID 32279727. https://doi.org/10.1016/j.pmr.2020.01.005
Witenko C, Moorman-Li R, Motycka C, et al. Considerations for the appropriate use of skeletal muscle relaxants for the management of acute low back pain. P T. 2014;39(6):427-435. PMID 25050056. https://pubmed.ncbi.nlm.nih.gov/25050056/
Medical disclaimer
This article is for educational purposes only and does not replace professional medical advice, diagnosis or treatment. Always talk to your doctor or pharmacist before starting, stopping or changing any medicine. If you think you or someone else is having a medical emergency, call your local emergency number right away.
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