Doctors recommend muscle relaxers for certain people with muscle pain and spasms. These drugs can provide short-term relief, but they can also cause side effects.

Muscle relaxers are not safe for everyone. Below, we describe the different types, recommended dosages for adults, and possible side effects. We also look into an over-the-counter (OTC) option and whether cannabis might help.

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Muscle relaxers encompass two classes of medications: antispasmodics and antispastics.

Antispastics directly affect the spinal cord or the skeletal muscles with the aim of improving muscle tightness and spasms.

Antispasmodics help reduce muscle spasms via the central nervous system. They inhibit the transmission of neurons in the brain.

Antispastics and antispasmodics have different indications and side effects. Since these drugs work differently, a person should never use them interchangeably or substitute one type for another.

While muscle relaxants may provide short-term relief of acute lower back pain and muscle spasms, these medications can cause adverse side effects. Some muscle relaxers can also be addictive.

For these reasons, a person should limit their use as much as possible.

Also, doctors and pharmacists may warn against using certain medications or consuming alcohol with muscle relaxers, as the interactions can be dangerous.

These muscle relaxers alter the conduction in the central nervous system to decrease muscle spasms.

There are two types of antispasmodics: benzodiazepines and nonbenzodiazepines.

Benzodiazepines block certain chemicals in the brain, and nonbenzodiazepines act on both the brain and spinal cord.

Diazepam

Diazepam is a benzodiazepine. Doctors may prescribe diazepam for severe muscle spasms and for spasticity associated with neurological disorders. Valium and Diastat are common brand names of this drug in the United States.

Doctors may recommend diazepam tablets or injections.

Dosage

DailyMed, an extension of the National Institutes of Health (NIH), report the dosage as 2–10 milligrams (mg) orally three or four times a day.

If someone requires diazepam injections, the doctor may prescribe an initial intravenous (IV) dose of 5–10 mg and another dose 3–4 hours later.

Side effects

Common side effects of diazepam include:

  • drowsiness
  • fatigue
  • muscle weakness
  • loss of muscle movement

There is a risk of severe drowsiness or sedation if a person takes this medication and an opioid. Other risks of combining a benzodiazepine with an opioid include respiratory failure, coma, and death.

Carisoprodol

Carisoprodol is a nonbenzodiazepine. Adults can take carisoprodol for the relief of acute, painful muscle conditions. A common brand name for this drug in the U.S. is Soma.

Doctors can only prescribe it for a maximum of 3 weeks. There is insufficient evidence that it works for longer periods.

Dosage

The recommended dosage is 250–300 mg three times a day and at bedtime.

Side effects

The most common side effects of carisoprodol include:

Drowsiness is a frequent side effect, and it can affect a person’s ability to drive or operate machinery.

Doctors also warn people of the dangers of combining this medication with alcohol. In addition, there is a risk of developing a dependency on carisoprodol.

Cyclobenzaprine

Cyclobenzaprine is a nonbenzodiazepine. It can treat muscle spasms that occur with acute muscle conditions when a person combines it with rest and physical therapy. Flexeril, Amrix, and Fexmid are brand names of this drug in the U.S.

Cyclobenzaprine comes in two oral forms: immediate-release tablets and extended-release capsules.

Dosage

DailyMed report that doctors usually prescribe 5 mg three times a day.

However, some people require higher dosages, such as 7.5 to 10.0 mg three times a day. The maximum is 30 mg per day.

Those taking the extended-release formula should take it at the same time each day.

Side effects

The most common side effects of cyclobenzaprine include:

  • dizziness
  • dry mouth
  • drowsiness
  • a headache
  • irritability
  • confusion

People taking medications that act on serotonin must avoid cyclobenzaprine, as it can increase the risk of developing serotonin syndrome, a potentially life-threatening condition.

Metaxalone

Metaxalone is a nonbenzodiazepine. Doctors prescribe metaxalone in combination with rest, physical therapy, and other nondrug treatment strategies for painful muscle conditions. The brand name of this drug is Skelaxin in the U.S.

Dosage

The recommended dosage for people over 12 years old is 800 mg three to four times a day.

Side effects

People taking metaxalone may experience:

People cannot take it with drugs that affect the amount of serotonin in the body, due to the risk of serotonin syndrome.

Below, find information about antispasmodics in a table:

DrugBrand nameFormDosage
DiazepamValiumTablet or injection2–10 mg three or four times a day (tablet), or
5–10 mg (injection)
CarisoprodolSomaTablet250–350 mg three times a day
CyclobenzaprineFlexerilTablet5–7.5 mg three times a day (tablet), or 15–30 mg once a day (extended-release capsule)
MetaxaloneSkelaxinCapsule800 mg three to four times a day

Antispastic medications work on the spinal cord or muscle cells.

These drugs can help with conditions that cause spasms, such as cerebral palsy or multiple sclerosis (MS), as well as spinal cord injuries.

Baclofen

The Food and Drug Administration (FDA) have approved baclofen for managing spasticity in people with:

  • flexor spasms
  • clonus
  • spinal cord lesions
  • MS

Doctors may recommend oral or intrathecal forms of baclofen. The latter involves an injection of the drug into the spinal canal.

The brand name of this medication is Lioresal in the U.S.

Dosage

Doctors typically recommend taking 5 mg tablets three times a day. The maximum oral dose is 80 mg per day.

If a person requires an intrathecal injection, they receive a single dose of 50 micrograms (mcg). If there is a response to the treatment, the doctor will adjust the dosage.

Side effects

The most common side effects of baclofen include:

  • drowsiness
  • confusion
  • muscle weakness
  • vertigo
  • nausea

Dantrolene

Dantrolene can help ease muscle spasticity. Brand names for this in the U.S. are Dantrium, Revonto, and Ryanodex.

Dosage

For muscle spasticity, doctors may prescribe 25 mg of dantrolene daily for 7 days.

They may then increase the dosage, depending on the person’s response. The maximum daily dosage is 400 mg.

IV dantrolene is also available.

Side effects

The side effects of IV dantrolene include breathing changes that occur due to weakness in the respiratory muscles and muscle weakness.

Oral dantrolene may damage the liver.

Tizanidine

Tizanidine has both antispasmodic and antispastic effects. People take it to help manage spasticity from MS or spinal cord injuries.

A brand name for this drug in the U.S. is Zanaflex.

Dosage

Doctors may prescribe capsules of 2, 4, or 6 mg. Or, they may prescribe tablets of 2 or 4 mg. People may take tizanidine every 6–8 hours as needed.

Side effects

People usually tolerate tizanidine well.

Some people report:

The following table contains information about antispastic medications.

DrugBrand nameFormDosage
BaclofenLioresalTablet, intrathecal injection5 mg, or 50 mcg as an initial dose, adjusted after 24 hours if needed
DantroleneDantriumTablet, injection25 mg once daily, increased by 25 mg until an effective dose is reached. The maximum is 400 mg per day
TizanidineZanaflexCapsule, tablet2, 4, or 6 mg (capsules), or 2 or 4 mg (tablets) every 6–8 hours

An OTC muscle relaxer does not require a prescription, but it may carry similar risks as a prescription muscle relaxer.

Methocarbamol

Methocarbamol is an OTC nonbenzodiazepine, antispasmodic medication. A common brand name for it in the U.S. is Robaxin.

People usually take this drug orally, but doctors can prescribe IV or intramuscular forms.

Dosage

If the doctor prescribes 500 mg tablets, they may recommend three tablets initially and two to maintain the effect. If they prescribe 750-mg tablets, they may recommend two initially and one or two to maintain the effect.

Overall, the guidelines advise taking 6 grams a day for the first 48–72 hours of treatment, though a doctor may recommend taking 8 grams in this period if the issue is severe.

Afterward, a doctor usually recommends lowering the dosage to about 4 grams a day.

Side effects

Side effects of methocarbamol may include:

  • dizziness
  • drowsiness
  • a headache
  • an upset stomach
  • confusion

Some research suggests that certain components in cannabis may have muscle relaxant effects.

Tetrahydrocannabinol (THC), the compound responsible for the inhibiting psychoactive effects of cannabis, may have muscle relaxant properties, for example.

Overall, however, there is very scarce evidence of this potential effect, possibly due to the widespread prohibition of the cultivation, supply, and possession of cannabis.

The legalization of cannabis across many jurisdictions will help researchers study its medical uses.

Anyone with muscle spasms and pain should consult a doctor, who may prescribe or recommend a muscle relaxer. It is important to be aware of the possible side effects.

While an OTC muscle relaxer exists, it may not be appropriate for all types of muscle conditions. Contact a doctor or speak with a pharmacist before taking any muscle relaxer.

Muscle relaxers help relieve muscle pain and spasms, but they can cause side effects. The best option depends on the injury or underlying condition and factors such as the person’s age and current medications.

There are risks involved in taking prescription or OTC muscle relaxers. Consult a doctor or pharmacist first and follow the instructions closely.