The Problem with Muscle Relaxants

If you are getting acceptable relief from non-drug approaches and OTC pain relievers, you will probably not need to add a prescription drug to the mix. And if you do need more pain relief, adding a muscle relaxant won’t necessarily help. In one study of 323 people showing up at an emergency room with low back pain, for example, neither an OTC NSAID (naproxen) plus a drug containing oxycodone and acetaminophen, or naproxen combined with the muscle relaxant cyclobenzaprine (Flexeril) provided better pain relief or improved function than naproxen alone. The patients were assessed at seven days and again three months after the emergency room visit.

However, in a 2019 study of 406 people with low back pain, researchers gave half the group a combination of ibuprofen and the muscle relaxant chlorzoxazone and the other half of the group ibuprofen alone. After seven days, people taking the drug combination experienced greater pain relief than those taking only ibuprofen. But the difference wasn’t huge — 94% of those on the combo regimen and 77% of the ibuprofen group reported a good to excellent response.

When a Muscle Relaxant Might Be Needed

Some people with a muscle pull, spasms or injury, or backache may need to take a muscle relaxant. They are:

  • People who can’t take acetaminophen or NSAIDs, or both, due to other medical conditions, and for whom a muscle relaxant may be preferable to an opioid painkiller.
  • People who don’t get sufficient pain relief from over-the-counter drugs.
  • People whose pain or discomfort prevents them from sleeping. The sedation associated with muscle relaxants may be helpful when the drug is taken at night.

Side Effects

Muscle relaxants cause a range of side effects that, as suggested above, warrant care when taking one. Side effects are common, and some people experience more than one of them. Common side effects include:

  • Sedation/drowsiness
  • Fatigue
  •  Clumsiness
  • Dizziness or light-headedness
  • Dry mouth
  • Confusion
  • Nausea
  • Headache
  • Lowered blood pressure

Call your doctor immediately if you experience any of the following:

  • Difficulty breathing
  • Weakness
  • Hives, rash or swelling of the face or tongue
  • Fast heart rate
  • Yellowing of the skin or eyes
  • Seizures


One problem is that people take muscle relaxants and expect to be able to function and work normally, including driving, operating machinery or doing cognitive tasks that require focus. As with opioids, muscle relaxants make all those tasks harder, even at low doses. And doing them while taking a muscle relaxant presents real risks of harm due to falls and accidents The package warnings that accompany the drugs warn against driving or operating machinery. You may think you can ignore that, but you shouldn’t.

Drinking is also discouraged while taking a muscle relaxant. This advice, too, is routinely ignored and shouldn’t be. Combining the two exacerbates, exponentially, poor functionality and mental acuity. It could also lead to life-threatening respiratory depression, or slowed breathing.


Muscle relaxants are not recommended for people 65 years or older — at all. There are a number of reasons for this. The side effects of the drugs are not tolerated well by older people, who are already at higher risk of falls and fractures. And in dosages that could be tolerated by older people, muscle relaxants probably wouldn’t be effective. Also, many people aged 65 and older take other medicines that could interact with muscle relaxants in adverse ways — again enhancing the risk of falls or other accidents.

Pregnant women should be sure to tell their doctor about the pregnancy before taking a muscle relaxant. For most of these drugs the risk to a fetus is unknown, but animal studies may have shown problems. As a rule, pregnant women are advised to take muscle relaxers only if they are clearly needed and the potential benefits outweigh the risks. People with a history of depression or substance abuse problems should also be sure to discuss this with their doctor.

Although most of the existing research doesn’t show any clear differences between the various muscle relaxants in the risk of different side effects they pose, a few of the drugs may be particularly problematic..

Carisoprodol (Soma) has been associated with a high risk of abuse and addiction potential. Carisoprodol breaks down in the body to form meprobamate, which is a controlled substance that has addictive properties and causes sedation.  Carisoprodol is classified as a controlled substance, due to its potential for abuse and reports from the Drug Abuse Warning Network (DAWN), the FDA’s Adverse Event Reporting System (AERS), and multiple other drug use surveys and reporting systems. The high number of reports of emergency visits attributable to the drug by the DAWN, including reports of coma and death, contributed to the drug’s designation as a controlled substance. Carisoprodol is the only muscle relaxant that is classified as a controlled substance.

Chlorzoxazone (Lorzone) has been associated with serious (including fatal) liver damage, although the incidence is rare. Even so, the drug should not be prescribed at all for people with liver disease or hepatitis.

Abuse of cyclobenzaprine (Amrix) is also a problem. From 2004 to 2011, the number of emergency room visits associated with the drug increased by 87%. That’s likely because it’s among the most prescribed muscle relaxants and because its generic formulation is one of the least expensive muscle relaxants.. Cyclobenzaprine should be used with caution by people with mild liver disease and avoided entirely in those with moderate to severe liver impairment.

The table below derives from a Consumer Reports report on muscle relaxants.

Selected Muscle Relaxants: Key Things to Know

Cyclobenzaprine (Flexeril)

  • Effectiveness supported by strongest body of evidence.
  • 5 mg as effective as 10 mg, with fewer side effects.
  • Should not be used by people with heart disease, arrhythmias, or glaucoma.

Cyclobenzaprine (Amrix)

  • Sustained-release formulation allows for once daily dosing.
  • Not found to be more effective than standard-release formulation
  • No generic available.
  • Should not be used by people with heart disease, arrhythmias, or glaucoma.

Carisoprodol (Soma)

  • Metabolized to meprobamate, a drug classified as a controlled substance because of abuse and addiction potential.
  • Case reports of abuse and addiction.
  • Avoid using the drug due to risk of addiction.

Chlorzoxazone (Lorzone)

    • Rare cases of liver toxicity.
    • May cause red-orange urine but this is not harmful.

Metaxalone (Skelaxin)

      • Should not be used by people with liver damage or kidney disease.

Methocarbamol (Robaxin, Robaxin-750)

      • May cause black, blue, or green urine, but this is not harmful.
      • Should not be used by people with liver disease.

Orphenadrine (Generic only)

    • Should not be used by people with liver disease, heart disease, arrhythmias, or glaucoma.

Source: Consumer Reports Best Buy Drugs

The Bottom Line

Avoid taking a muscle relaxant if non-drug approaches or OTC drugs reduce your discomfort and pain. If you have to take one, tell your doctor about all the other drugs you’re taking, take the muscle relaxants with great care, at the lowest dose possible, and preferably at night. Don’t take it for any longer than necessary. There’s little evidence to show that long-term use improves symptoms.

If you have muscle spasms or back pain that does not resolve in a week or so, or flares up from time to time, ask your doctor for a referral to a physical therapist or a specialist. Taking muscle relaxants has not been shown effective in the long-term treatment of back pain. Neither have opioid painkillers.

For more on using medications safely:

Think it Through: Managing the Benefits and Risks of Medicines

Sprains and Strains

Real Pain Relief, Now!

More from MedShadow:

Pain in the Back

Can the Pain Without the Meds: 8 Non-Pharma Therapies


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