Skip to Content

Methocarbamol

Pronunciation

Pronunciation

(meth oh KAR ba mole)

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Solution, Injection:

Robaxin: 1000 mg/10 mL (10 mL [DSC])

Robaxin: 1000 mg/10 mL (10 mL) [contains polyethylene glycol 300]

Solution, Injection [preservative free]:

Generic: 1000 mg/10 mL (10 mL)

Tablet, Oral:

Robaxin: 500 mg [scored; contains fd&c yellow #6 (sunset yellow), saccharin sodium]

Robaxin-750: 750 mg [contains fd&c yellow #10 (quinoline yellow), fd&c yellow #6 (sunset yellow), saccharin sodium]

Generic: 500 mg, 750 mg

Brand Names: U.S.

  • Robaxin
  • Robaxin-750

Pharmacologic Category

  • Skeletal Muscle Relaxant

Pharmacology

Causes skeletal muscle relaxation by general CNS depression

Metabolism

Hepatic via dealkylation and hydroxylation

Excretion

Urine (primarily as metabolites)

Onset of Action

Muscle relaxation: Oral: ~30 minutes

Time to Peak

Serum: Oral: 1-2 hours

Half-Life Elimination

1-2 hours

Protein Binding

46% to 50%

Special Populations: Renal Function Impairment

Cl is decreased approximately 40% in patients with severe renal impairment.

Special Populations: Hepatic Function Impairment

Cl is decreased approximately 70%; t1/2 is prolonged ~ 3-fold in cirrhosis patients.

Use: Labeled Indications

Adjunctive treatment of muscle spasm associated with acute painful musculoskeletal conditions (eg, tetanus)

Contraindications

Hypersensitivity to methocarbamol or any component of the formulation; renal impairment (injection formulation)

Dosage

Tetanus: IV:

Children: Recommended only for use in tetanus: 15 mg/kg/dose or 500 mg/m2/dose, may repeat every 6 hours if needed; maximum dose: 1.8 g/m2/day for 3 days only

Adults: Initial dose: 1-2 g by direct IV injection, which may be followed by an additional 1-2 g by infusion (maximum initial dose: 3 g total); followed by 1-2 g every 6 hours until oral administration by mouth or via NG tube is possible; total oral daily doses of up to 24 g may be needed; injection should not be used for more than 3 consecutive days

Muscle spasm:

Oral: Children ≥16 years and Adults: 1.5 g 4 times/day for 2-3 days (up to 8 g/day may be given in severe conditions), then decrease to 4-4.5 g/day in 3-6 divided doses

IM, IV: Adults: Initial: 1 g; may repeat every 8 hours if oral administration not possible; maximum dose: 3 g/day for no more than 3 consecutive days. If condition persists, may repeat course of therapy after a drug-free interval of 48 hours.

Dosage adjustment in renal impairment: No dosage adjustment provided in manufacturer’s labeling. However, administration of the parenteral formulation is contraindicated in patients with renal dysfunction due to the presence of polyethylene glycol.

Dosage adjustment in hepatic impairment: No dosage adjustment provided in manufacturer’s labeling. However, elimination may be reduced in patients with cirrhosis.

Reconstitution

Solution for injection: May administer undiluted or diluted in D5W or NS (1 vial/≤250 mL diluent).

Administration

Solution for injection:

IM: A maximum of 5 mL can be administered into each gluteal region.

IV: Maximum rate: 3 mL/minute; may be administered undiluted or diluted. Monitor closely for extravasation. Administer IV while in recumbent position. Maintain position for at least 10-15 minutes following infusion.

Tablet: May be crushed and mixed with food or liquid if needed.

Storage

Solution for injection: Prior to dilution, store at controlled room temperature of 20°C to 25°C (68°F to 77°F); excursions permitted to 15°C to 30°C (59°F to 86°F).

Tablet: Store at controlled room temperature of 20°C to 25°C (68°F to 77°F).

Drug Interactions

Alcohol (Ethyl): CNS Depressants may enhance the CNS depressant effect of Alcohol (Ethyl). Monitor therapy

Azelastine (Nasal): CNS Depressants may enhance the CNS depressant effect of Azelastine (Nasal). Avoid combination

Brimonidine (Topical): May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Buprenorphine: CNS Depressants may enhance the CNS depressant effect of Buprenorphine. Management: Consider reduced doses of other CNS depressants, and avoiding such drugs in patients at high risk of buprenorphine overuse/self-injection. Initiate buprenorphine patches (Butrans brand) at 5 mcg/hr in adults when used with other CNS depressants. Consider therapy modification

Cannabis: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

CNS Depressants: May enhance the adverse/toxic effect of other CNS Depressants. Exceptions: Levocabastine (Nasal). Monitor therapy

Doxylamine: May enhance the CNS depressant effect of CNS Depressants. Management: The manufacturer of Diclegis (doxylamine/pyridoxine), intended for use in pregnancy, specifically states that use with other CNS depressants is not recommended. Monitor therapy

Dronabinol: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Droperidol: May enhance the CNS depressant effect of CNS Depressants. Management: Consider dose reductions of droperidol or of other CNS agents (e.g., opioids, barbiturates) with concomitant use. Consider therapy modification

Eperisone: May enhance the adverse/toxic effect of Methocarbamol. Monitor therapy

Hydrocodone: CNS Depressants may enhance the CNS depressant effect of Hydrocodone. Management: Consider starting with a 20% to 30% lower hydrocodone dose when using together with any other CNS depressant. Dose reductions in the other CNS depressant may also be warranted. Consider therapy modification

HydrOXYzine: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Kava Kava: May enhance the adverse/toxic effect of CNS Depressants. Monitor therapy

Magnesium Sulfate: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Methotrimeprazine: CNS Depressants may enhance the CNS depressant effect of Methotrimeprazine. Methotrimeprazine may enhance the CNS depressant effect of CNS Depressants. Management: Reduce adult dose of CNS depressant agents by 50% with initiation of concomitant methotrimeprazine therapy. Further CNS depressant dosage adjustments should be initiated only after clinically effective methotrimeprazine dose is established. Consider therapy modification

Metyrosine: CNS Depressants may enhance the sedative effect of Metyrosine. Monitor therapy

Minocycline: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Mirtazapine: CNS Depressants may enhance the CNS depressant effect of Mirtazapine. Monitor therapy

Nabilone: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Orphenadrine: CNS Depressants may enhance the CNS depressant effect of Orphenadrine. Avoid combination

Paraldehyde: CNS Depressants may enhance the CNS depressant effect of Paraldehyde. Avoid combination

Perampanel: May enhance the CNS depressant effect of CNS Depressants. Management: Patients taking perampanel with any other drug that has CNS depressant activities should avoid complex and high-risk activities, particularly those such as driving that require alertness and coordination, until they have experience using the combination. Consider therapy modification

Pramipexole: CNS Depressants may enhance the sedative effect of Pramipexole. Monitor therapy

Pyridostigmine: Methocarbamol may diminish the therapeutic effect of Pyridostigmine. Monitor therapy

ROPINIRole: CNS Depressants may enhance the sedative effect of ROPINIRole. Monitor therapy

Rotigotine: CNS Depressants may enhance the sedative effect of Rotigotine. Monitor therapy

Rufinamide: May enhance the adverse/toxic effect of CNS Depressants. Specifically, sleepiness and dizziness may be enhanced. Monitor therapy

Selective Serotonin Reuptake Inhibitors: CNS Depressants may enhance the adverse/toxic effect of Selective Serotonin Reuptake Inhibitors. Specifically, the risk of psychomotor impairment may be enhanced. Monitor therapy

Sodium Oxybate: May enhance the CNS depressant effect of CNS Depressants. Management: Consider alternatives to combined use. When combined use is needed, consider minimizing doses of one or more drugs. Use of sodium oxybate with alcohol or sedative hypnotics is contraindicated. Consider therapy modification

Suvorexant: CNS Depressants may enhance the CNS depressant effect of Suvorexant. Management: Dose reduction of suvorexant and/or any other CNS depressant may be necessary. Use of suvorexant with alcohol is not recommended, and the use of suvorexant with any other drug to treat insomnia is not recommended. Consider therapy modification

Tapentadol: May enhance the CNS depressant effect of CNS Depressants. Management: Start tapentadol at a dose of one-third to one-half of the normal dose if being initiated in a patient who is taking another drug with CNS depressant effects. Monitor closely for evidence of excessive CNS depression. Consider therapy modification

Tetrahydrocannabinol: May enhance the CNS depressant effect of CNS Depressants. Monitor therapy

Thalidomide: CNS Depressants may enhance the CNS depressant effect of Thalidomide. Avoid combination

Zolpidem: 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. Consider therapy modification

Test Interactions

May cause color interference in certain screening tests for 5-HIAA using nitrosonaphthol reagent and in screening tests for urinary VMA using the Gitlow method.

Adverse Reactions

Frequency not defined.

Cardiovascular: Bradycardia, flushing, hypotension, syncope

Central nervous system: Amnesia, confusion, coordination impaired (mild), dizziness, drowsiness, fever, headache, insomnia, lightheadedness, sedation, seizures, vertigo

Dermatologic: Angioneurotic edema, pruritus, rash, urticaria

Gastrointestinal: Dyspepsia, metallic taste, nausea, vomiting

Hematologic: Leukopenia

Hepatic: Jaundice

Local: Pain at injection site, thrombophlebitis

Ocular: Blurred vision, conjunctivitis, diplopia, nystagmus

Respiratory: Nasal congestion

Miscellaneous: Hypersensitivity reactions including anaphylaxis

Warnings/Precautions

Concerns related to adverse effects:

• CNS depression: May cause CNS depression, which may impair physical or mental abilities; patients must be cautioned about performing tasks which require mental alertness (eg, operating machinery or driving).

Disease-related concerns:

• Hepatic impairment: Plasma protein binding and clearance are decreased and the half-life is increased in patients with hepatic impairment.

• Renal impairment: Use of IV formulation is contraindicated.

• Seizure disorder: Use injection with caution in patients with a history of seizure disorder.

Concurrent drug therapy issues:

• Sedatives: Effects may be potentiated when used with other sedative drugs or ethanol.

Special populations:

• Elderly: Muscle relaxants are poorly tolerated by the elderly due to potent anticholinergic effects, sedation, and risk of fracture. Efficacy is questionable at dosages tolerated by elderly patients; avoid use (Beers Criteria).

• Pediatric: IV formulation: Recommended only for the treatment of tetanus in pediatric patients.

Dosage form specific issues:

• Injection: Contraindicated in renal impairment. Contains polyethylene glycol. Rate of injection should not exceed 3 mL/minute; solution is hypertonic; avoid extravasation. Vial stopper contains latex.

Monitoring Parameters

Monitor closely for extravasation (IV administration).

Pregnancy Risk Factor

C

Pregnancy Considerations

Animal reproduction studies have not been conducted. The manufacturer notes that fetal and congenital abnormalities have been rarely reported following in utero exposure. Use during pregnancy only if clearly needed.

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience nausea, fatigue, headache, insomnia, rhinitis, dysgeusia, or injection site pain or irritation. Have patient report immediately to prescriber severe asthenia, jaundice, significant dizziness, syncope, bradycardia, chills, pharyngitis, memory impairment, illogical thinking, vision changes, or involuntary eye movements (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating and advising patients.

Hide