Methocarbamol (Robaxin) Tablets/ Injection - Uses, Dosage, Side effects

A centrally acting muscle relaxant is methocarbamol (Robaxin). 

In addition to physical therapy and painkillers, it is used to treat severe painful spasms.

It is available as 500 mg and 750 mg oral tablets and as injections for intravenous and intramuscular use.

Methocarbamol (Robaxin) Uses:

  • This medicine helps ease muscle spasms that happen because of really painful muscle and bone diseases.
  • It works well for people with recent back pain and muscle spasms but might not be as useful for those with long-term issues like cerebral palsy.
  • It doesn't work as well for conditions with joint inflammation, like gout and arthritis, because these are caused by joint problems, not muscle spasms.

Methocarbamol (Robaxin) Dose in adults:

Methocarbamol (Robaxin) Dose in the treatment of Muscle spasm:

  • Oral Tablets:

  • Take 1.5 grams by mouth four times a day for 2-3 days. In severe cases, you might be given up to 8 grams per day.
  • Then, the dose is reduced to 4-4.5 grams per day, spread out over 3-6 doses.
  • Intramuscular, Intravenous Formulation:

  • Initially, receive 1 gram.
  • This dose can be repeated every eight hours if you can't take the medicine by mouth.
  • The maximum dose is 3 grams per day, but not for more than three days in a row.
  • After going 48 hours without using any drugs, the treatment can be repeated if the situation hasn't improved.

Methocarbamol (Robaxin) Dose in the treatment of Tetanus:

  • Start with an initial dose of 1-2 grams through direct IV injection, followed by an additional 1-2 grams through IV infusion.

  • The total maximum initial dose should not exceed 3 grams.

  • If using a nasogastric tube or oral treatment is not possible, you can give the initial dose once every six hours until it's feasible.

  • The total dose may go up to 24 grams.

  • Wait for a maximum of three consecutive days before giving the injection again.

Methocarbamol (Robaxin) Dose in Childrens:

Methocarbamol (Robaxin) Dose in the treatment of Muscle spasm:

  • Adolescents older than 16 years:

    • Take 1,500 milligrams by mouth four times a day for 2 to 3 days.

    • The highest amount you should take in one day is 8 grams, which is typically used for severe conditions.

    • After the initial period, decrease the dose to 4,000 to 4,500 milligrams per day, spread out in 3 to 6 doses.

    • For example, you might take 1,000 milligrams four times a day or 750 milligrams every four hours or 1,500 milligrams three times a day.

Methocarbamol (Robaxin) Dose in the treatment of Tetanus:


  • Consider using alternative medications like benzodiazepines.
  • Infants, Children, and Adolescents:

    • Administer 15 mg per kilogram of body weight or 500 mg per square meter of body surface area intravenously.
    • If needed, the dose can be repeated every six hours.
    • The typical adult dose is 1,000 to 2,000 mg per dose.
    • The maximum total dose should not exceed 1.8 grams per square meter over three days.
    • It is not advisable to use the injection for more than three consecutive days in adults.

Pregnancy Risk Category: C

  • The medication has not undergone testing on pregnant animals or humans.

  • There is a connection between exposure during pregnancy and the occurrence of congenital and fetal abnormalities.

Use of methocarbamol while breastfeeding

  • We don't know if the drug can pass into breast milk.

  • Manufacturers advise lactating women to use the drug cautiously.

Methocarbamol (Robaxin) Dose in Kidney Disease:

  • According to the manufacturer's label, patients with kidney disease should not receive dose adjustments.

  • Additionally, the injection, which contains polyethylene glycol, is not suitable for patients with kidney disease.

Methocarbamol (Robaxin) Dose in Liver disease:

  • The manufacturer's instructions do not recommend adjusting the dose.
  • However, in patients with cirrhosis, the half-life of the drug is prolonged.

Side effects of Methocarbamol (Robaxin):

  • Cardiovascular:

    • Bradycardia
    • Flushing
    • Hypotension
    • Syncope
    • Thrombophlebitis
  • Central Nervous System:

    • Amnesia
    • Ataxia
    • Confusion
    • Dizziness
    • Drowsiness
    • Headache
    • Insomnia
    • Metallic Taste
    • Sedation
    • Seizure
    • Vertigo
  • Dermatologic:

    • Pruritus
    • Skin Rash
    • Urticaria
  • Gastrointestinal:

    • Dyspepsia
    • Nausea
    • Vomiting
  • Hematologic & Oncologic:

    • Leukopenia
  • Hepatic:

    • Cholestatic Jaundice
    • Jaundice
  • Hypersensitivity:

    • Anaphylaxis
    • Angioedema
    • Hypersensitivity Reaction
  • Local:

    • Local Skin Exfoliation (Injection)
    • Pain At Injection Site
  • Ophthalmic:

    • Blurred Vision
    • Conjunctivitis
    • Diplopia
    • Nystagmus
  • Respiratory:

    • Nasal Congestion
  • Miscellaneous:

    • Fever

Contraindications to Methocarbamol (Robaxin):

  • Avoid the drug if there are allergic reactions to any of its components or to the drug itself.
  • The injection formulation is not recommended for individuals with kidney disease.

Warnings and precautions

  • Depression in the CNS:

  • It can lead to depression in the central nervous system.
  • People who need to stay alert, such as those driving or operating heavy machinery, should use the drug cautiously.
  • Hepatic impairment
    • In individuals with liver disease, there is a reduced binding of the drug to plasma proteins, leading to decreased drug clearance and a longer half-life.

  • Renal impairment

    • Individuals with kidney impairment should refrain from receiving intravenous injections.

  • Seizure disorder

    • Individuals with seizure disorders should steer clear of intravenous administration.
    • For the oral formulation, those with seizure disorders may need to exercise caution.

Methocarbamol: Drug Interaction

Risk Factor C (Monitor therapy)

Alcohol (Ethyl)

Alcohol's CNS depressing effect may be amplified by CNS depressants (Ethyl).


CNS depressants may have an enhanced CNS depressant impact.

Botulinum Toxin-Containing Products

Centrally acting muscle relaxants may intensify the harmful/toxic effects of products containing  botulinum  toxin. In particular, there may be a greater likelihood of developing muscle  weakness.


Brexanolone's CNS depressing effects may be amplified by other CNS depressants.

Brimonidine (Topical)

CNS depressants may have an enhanced CNS depressant impact.


CNS depressants may have an enhanced CNS depressant impact.


CNS depressants may have an enhanced CNS depressant impact.


CNS depressants may have an enhanced CNS depressant impact.

Chlorphenesin Carbamate

CNS depressants may have an enhanced CNS depressant impact.

CNS Depressants

CNS depressants may have an enhanced CNS depressant impact.

Dimethindene (Topical)

CNS depressants may have an enhanced CNS depressant impact.


CNS depressants may have an enhanced CNS depressant impact. Management: The producer of the pregnancy-safe drug Diclegis (doxylamine/pyridoxine) particularly advises against combining it with other CNS depressants.


CNS depressants may have an enhanced CNS depressant impact.


Could make methocarbamol's negative or hazardous effects worse.


CNS depressants may have an enhanced CNS depressant impact.


CNS depressants may have an enhanced CNS depressant impact.

Kava Kava

CNS depressants may have an enhanced CNS depressant impact.


May enhance the adverse/toxic effect of Methocarbamol.

Magnesium Sulfate

CNS depressants may have an enhanced CNS depressant impact.


CNS Depressants may enhance the sedative effect of MetyroSINE.

Minocycline (Systemic

CNS depressants may have an enhanced CNS depressant impact.


CNS depressants may have an enhanced CNS depressant impact.


Piribedil's CNS depressing effects may be enhanced by other CNS depressants.


The sedative effects of pramipexole might be enhanced by CNS depressants.


.Methocarbamol may reduce Pyridostigmine's therapeutic effect.


The sedative effects of CNS depressants may increase those of ROPINIRole.


Rotigotine's sedative effects may be boosted by CNS depressants.


CNS depressants' harmful or toxic effects could be increased. Particularly, drowsiness and lightheadedness could be  worsened.

Selective Serotonin Reuptake Inhibitors

Selective serotonin reuptake inhibitors may have a worsened or more hazardous effect when taken with CNS  depressants. Particularly, there may be an increased risk of psychomotor impairment.


CNS depressants may have an enhanced CNS depressant impact.

Tetrahydrocannabinol and Cannabidiol

CNS depressants may have an enhanced CNS depressant impact.


CNS depressants may have an enhanced CNS depressant impact.

Risk Factor D (Consider therapy modification)


Blonanserin's CNS depressing effects may be enhanced by other CNS depressants.


The CNS depressing impact of buprenorphine may be enhanced by CNS depressants. Treatment: If a patient  has a high risk of abusing or injecting themselves with buprenorphine, consider reducing  the doses of other  CNS depressants and avoiding such medications. Buprenorphine should be started at lower doses in individuals  who are currently taking CNS depressants.


CNS depressants may have an enhanced CNS depressant impact. Management: Keep a close eye out for signs of  severe CNS depression. If such a combination is required, it should be taken at a dose that has been suitably  lowered,  according to the instructions for chlormethiazole.


CNS depressants may have an enhanced CNS depressant impact. Consider lowering the dosage of droperidol or  other CNS drugs (such as opioids or barbiturates) when they are used concurrently. In separate  drug interaction  monographs, exceptions to this monograph are covered in more detail.


Flunitrazepam's CNS depressing effects may be enhanced by other CNS depressants.


The CNS depressive action of HYDROcodone may be enhanced by CNS depressants. Management: Whenever  feasible,  refrain from using hydrocodone and benzodiazepines or other CNS depressants concurrently. Only in the  event that other treatment choices are insufficient should these medications be combined. Limit the  duration  and dosage of each medicine when used together.


CNS depressants may have an enhanced CNS depressant impact. Management: Due to the possibility of additive  CNS  depressant effects when lemborexant and concurrent CNS depressants are administered concurrently,  dosage modifications may be required. Effects of CNS depressants must be closely monitored.


The CNS depressing action of methotrimeprazine may be enhanced by CNS depressants. The CNS depressant action  of  CNS  Depressants may be strengthened by methotrimeprazine. Management: Start concurrent methotrimeprazine  therapy while  reducing  the adult dose of CNS depressants by 50%. Only once a clinically effective dose of  methotrimeprazine  has been established  should additional CNS  depressant dosage modifications be made.

Opioid Agonists

Opioid agonists' CNS depressing effects may be amplified by CNS depressants. Management: When at all possible,  refrain from using benzodiazepines or other CNS depressants concurrently with opioid agonists. Only in the  event that other treatment choices are insufficient should these medications be combined. Limit the duration and  dosage of each medicine when used together.


The CNS depressing effects of OxyCODONE may be enhanced by CNS depressants. Management: Whenever  feasible,  refrain from using oxycodone and benzodiazepines or other CNS depressants concurrently. Only in the  event  that other treatment choices are insufficient should these medications be combined. Limit the duration  and dosage of each medicine when used together.


CNS depressants may have an enhanced CNS depressant impact. Treatment: Until they have experience using  the combination, patients  taking perampanel along  with any other medication that has CNS depressive  effects  should avoid complex and high-risk activities, especially those like driving that call for awareness and  coordination.

Sodium Oxybate

CNS depressants may have an enhanced CNS depressant impact. Management: Take into account substitutes for  combined use. Reduce the doses of one or more medications when simultaneous use is necessary. It is not  advised to use sodium oxybate with alcoholic beverages or hypnotic sedatives.


Suvorexant's CNS depressing effects may be amplified by other CNS depressants. Treatment: Suvorexant and/or  any other CNS depressant dosage reduction may be required. Suvorexant shouldn't be taken with alcohol,  and it  shouldn't be taken for sleeplessness with any other medication either.


CNS depressants may have an enhanced CNS depressant impact. Treatment: When feasible, refrain from using  tapentadol and benzodiazepines or other CNS depressants simultaneously. Only in the event that other  treatment  choices are insufficient should these medications be combined. Limit the duration and dosage of each medicine  when used together.


May intensify the negative or harmful effects of muscle relaxants (Centrally Acting). Management: If tolperisone is  used  with  other centrally acting muscle relaxants, watch for signs of increased sedation or CNS effects. If these  medications  are taken together, think about lowering the tolperisone dosage.


CNS Depressants may enhance the CNS depressant effect of Zolpidem. Management: Reduce the Intermezzo brand sublingual zolpidem adult dose to 1.75 mg for men who are also receiving other CNS depressants. No such dose change is recommended for women. Avoid use with other CNS depressants at bedtime; avoid use with alcohol.

Risk Factor X (Avoid combination)

Azelastine (Nasal)

Azelastine's CNS depressing impact may be amplified by CNS depressants (Nasal).


CNS depressants may have an enhanced CNS depressant impact.


Azelastine's CNS depressing impact may be amplified by CNS depressants (Nasal).


CNS depressants may have an enhanced CNS depressant impact.


The CNS depressing effects of paraldehyde may be enhanced by CNS depressants.


The CNS depressing effect of thalidomide may be enhanced by CNS depressants.


Monitoring parameters:

Keep a close watch on the injection site for signs of extravasation (leakage of the injected substance into the surrounding tissues).

Additionally, monitor the site for any occurrences of bradycardia (slow heart rate) and hypotension (low blood pressure) after intravenous administration.

How to administer Methocarbamol (Robaxin)?

For the solution for injection:

Intramuscular Injection:

  • Administer in the gluteal area.
  • Each gluteal area can receive a maximum of 5 mL.

Intravenous Injection:

  • Ensure the maximum injection rate does not exceed 3 mL per minute.
  • You can administer the injection undiluted or diluted.
  • Monitor for extravasation at the injection site.
  • Administer the injection intravenously while the patient is lying down.
  • After the infusion, the patient should remain in a reclined position for 10 to 15 minutes.


  • If needed, the tablets can be broken up and mixed with liquids or food.

Mechanism of action of Methocarbamol (Robaxin):

It induces central nervous system depression, leading to the relaxation of skeletal muscles.

Details after oral administration:

  • Onset of muscle relaxation: Approximately 30 minutes
  • Protein binding: 46% to 50%
  • Metabolism: It undergoes metabolism in the liver through dealkylation and hydroxylation.
  • Elimination half-life: 1 to 2 hours
  • Time to reach peak serum concentration after oral administration: 1 to 2 hours
  • Excretion: It is primarily eliminated in the urine as metabolites.

International Brands of Methocarbamol:

  • Robaxin
  • Robaxin-750
  • Methocarbamol Omega
  • PMS-Methocarbamol
  • Robaximol
  • Bolaxin
  • Carbamol
  • Lumirelax
  • Manobaxine
  • Methocarbamol
  • Metocamol
  • Mibelaxol
  • Miowas
  • Musxan
  • Myomethol
  • Myorexin Inj
  • New-Rexan
  • Ortoton
  • Rebamol
  • Rexivin
  • Robinax

Methocarbamol Brand Names in Pakistan:

No Brands Available in Pakistan.