Robaxin vs. Flexeril

  • Medical Editor: John P. Cunha, DO, FACOEP
    John P. Cunha, DO, FACOEP

    John P. Cunha, DO, FACOEP

    John P. Cunha, DO, is a U.S. board-certified Emergency Medicine Physician. Dr. Cunha's educational background includes a BS in Biology from Rutgers, the State University of New Jersey, and a DO from the Kansas City University of Medicine and Biosciences in Kansas City, MO. He completed residency training in Emergency Medicine at Newark Beth Israel Medical Center in Newark, New Jersey.

What are the differences between Robaxin and Flexeril?

  • Robaxin (methocarbamol) and Flexeril (cyclobenzaprine) are skeletal muscle relaxants.
  • The brand name Flexeril has been discontinued in the U.S. Amrix and Fexmid are the brand names available for cyclobenzaprine in the U.S.
  • Both Robaxin and Flexeril are available in generic form.
  • Side effects of Robaxin and Flexeril that are similar include drowsiness, dizziness, headache, nausea, and vomiting.
  • Side effects of Robaxin that are different from Flexeril include lightheadedness, confusion, flushing, and lowered heart rate.
  • Side effects of Flexeril that are different from Robaxin include dry mouth, fatigue, constipation, blurred vision, unpleasant taste, nervousness, confusion, acid reflux, and abdominal pain or discomfort.
  • Both Robaxin and Flexeril may interact with narcotic painkillers, alcohol, sedative or hypnotic medications, and other medications that depress the central nervous system.
  • Flexeril is chemically related to the tricyclic class of antidepressants, and should not be taken with or within two weeks of monoamine oxidase (MAO) inhibitors.
  • Suddenly stopping Flexeril after prolonged therapy may cause withdrawal symptoms such as headaches, nausea, and weakness.

What are Robaxin and Flexeril?

Robaxin (methocarbamol) is a skeletal muscle relaxant with sedative effects. The exact mechanism of how methocarbamol works is not known. Robaxin is presumed to work by depressing the central nervous system, leading to relaxation of muscles. Robaxin is prescribed for the relief of discomfort associated with painful skeletal muscle spasms. Robaxin is also used for relief from tetanus spasms.

Flexeril (cyclobenzaprine) is a skeletal muscle relaxant. Flexeril is used with rest and physical therapy for short-term relief of muscle spasms associated with acute painful muscle and skeletal conditions. It is only for short-term use, up to two or three weeks.

What are the side effects of Robaxin and Flexeril?

Robaxin

Common side effects of methocarbamol include:

Flexeril

The most common side effects of cyclobenzaprine include:

Other reported side effects include:

Possible serious side effects include:

Abrupt cessation after prolonged therapy may cause withdrawal symptoms such as headaches, nausea, and weakness.

What is the dosage of Robaxin and Flexeril?

Robaxin

Musculoskeletal pain in adults:

  • Initially, take three 500 mg tablets by mouth 4 times a day for first 48 to 72 hours, then take 2 tablets by mouth 4 times a day for the maintenance of spasms.
  • If using 750 mg tablets take 2 tablets by mouth 4 times a day for the first 48 to 72 hours, then take 1 tablet by mouth every 4 hours or take 2 tablets by mouth 3 times a day for the maintenance of spasms.
  • The dose for injections is 1 gram intravenously or intramuscularly every 8 hours with a maximum dose of 3 grams per day for 3 days.
    • If needed, the same course may be repeated after a 48 hour drug free interval.

Tetanus spasms:

  • Adults: Inject 1 to 2 grams intravenously every 6 hours as needed with a maximum dose of 24 grams per day.
  • Children: Inject 15 mg/kg intravenously every 6 hours as needed.
    • The total dose should not exceed 1.8 g/m2 for 3 consecutive days.

Flexeril

The recommended dose of cyclobenzaprine dose is 5 or 10 mg three times daily using immediate release tablets or 15 or 30 mg once daily using extended release tablets.

What drugs interact with Robaxin and Flexeril?

Robaxin

Methocarbamol can increase sedation if taken with narcotic painkillers, alcohol, sedative or hypnotic medications, and other medications that depress the central nervous system. Loss of consciousness, troubled breathing, lowered heart rate, and in severe cases death or coma can also occur.

Flexeril

Cyclobenzaprine is chemically related to the tricyclic class of antidepressants, for example, amitriptyline (Elavil, Endep), nortriptyline Pamelor). As such, it should not be taken with or within two weeks of any monoamine oxidase (MAO) inhibitor, for example, isocarboxazid (Marplan), phenelzine (Nardil), tranylcypromine (Parnate), and procarbazine (Matulane). High fever, convulsions, and even death can occur when these drugs are used together.

Cyclobenzaprine interacts with other medications and drugs that slow the brain's processes, such as

Are Robaxin and Flexeril safe to take while pregnant or breastfeeding?

Robaxin

There are no adequate studies of methocarbamol to determine safe and effective use in pregnant women. Methocarbamol should be avoided in pregnant mothers to avoid any risk to the unborn.

It is not known whether methocarbamol enters breast milk. It should be avoided in nursing mothers to prevent any adverse effects to the newborn.

Flexeril

There are no adequate studies of cyclobenzaprine in pregnant women. However, studies in animals suggest no important effects on the fetus. Cyclobenzaprine therefore can be used in pregnancy if the physician feels that it is necessary.

It is not known whether cyclobenzaprine is secreted in milk. However, since it is related to the tricyclic antidepressants, some of which are excreted in breast milk, caution is advised in using this medication in women who are breastfeeding.

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Medically Reviewed on 11/1/2017
References
FDA Prescribing Information
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