MUSCLAX

Methocarbamol was developed in the early 1950s as a treatment for muscle spasticity and the associated pain. 6, 7 It is a guaiacol glyceryl ether.

Methocarbamol tablets and intramuscular injections are prescription medicines indicated in the United States as an adjunct to rest, physical therapy, and other measures for the relief of discomforts associated with acute, painful musculoskeletal conditions.

Label, 9 In Canada, methocarbamol can be sold as an over the counter oral medicine at a lower dose that may be combined with acetaminophen or ibuprofen.

A with acetylsalicylic acid and codeine is available in Canada by prescription.

Methocarbamol was

FDA approved on 16 July 1957.

Methocarbamol tablets and intramuscular injections are indicated in the United States as an adjunct to rest, physical therapy, and other measures for the relief of discomforts associated with acute, painful musculoskeletal conditions.

Label, 9 Oral methocarbamol in America may be given up to 1500 mg 4 times daily for 2-3 days.

In Canada, methocarbamol containing oral formulations are sold over the counter for pain associated with muscle spasm.

However, if these combination formulations include codeine, they are prescription only.

Methacarbamol is a skeletal muscle relaxant with an unknown mechanism of action.

Methacarbamol has been shown to block spinal polysynaptic reflexes, decrease nerve transmission in spinal and supraspinal polysynaptic pathways, and prolong the refractory period of muscle cells. 5, 4 Methocarbamol does not act as a local anesthetic upon injection.

In animal studies, methocarbamol also prevents convulsions after electric shock.

The mechanism of action of methocarbamol is thought to be dependant on its central nervous system depressant activity.

This action may be mediated through blocking spinal polysynaptic reflexes, decreasing nerve transmission in spinal and supraspinal polysynaptic pathways, and prolonging the refractory period of muscle cells. 5, 4 Methocarbamol has been found to have no effect on contraction of muscle fibres, motor end plates, or nerve fibres.

Carbonic anhydrase 1 inhibitor Humans.

The time to maximum concentration is 1.1 hours for both healthy patients and those on hemodialysis.

The maximum plasma concentration is 21.3 mg/L for healthy patients and 28.7 mg/L in hemodialysis patients.

The area under the curve for healthy patients is 52.5 mg/Lhr and 87.1 mg/Lhr in hemodialysis patients.

AUC% based on terminal elimination half life is 2% for healthy patients and 4% for hemodialysis patients.

Older studies report maximum plasma concentrations in 0.5 hours.

data in humans is scarce.

In horses, the volume of distribution is 515-942 mL/kg at steady state or 724-1130 mL/kg.

Methocarbamol is metabolized in the liver by demethylation to 3-(2-hydroxyphenoxy)-1,2-propanediol-1-carbamate or hydroxylation to 3-(4-hydroxy-2-methoxyphenoxy)-1,2-propanediol-1-carbamate.

Methocarbamol and its metabolites are conjugated through glucuronidation or sulfation.

Hover over products below to view reaction partners Methocarbamol 3-(2-hydroxyphenoxy)-1,2-propanediol-1-carbamate 3-(4-hydroxy-2-methoxyphenoxy)-1,2-propanediol-1-carbamate.

In humans the majority of the dose is eliminated in the urine.

In dogs, 88.85% of the dose is eliminated in urine and 2.14% in the feces.

In rats, 84.5-92.5% of the dose is eliminated in the urine and 0-13.3% is eliminated in the feces.

The elimination half life is 1.14 hours in healthy subjects and 1.24 hours in subjects with renal insufficiency.

Older studies report half lives of 1.6-2.15 hours.

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Overdose of methocarbamol may be associated with alcohol and other central nervous system depressants.

Patients may experience nausea, drowsiness, blurred vision, hypotension, seizures, and coma.

Treatment of overdose is generally through airway maintenance, monitoring urinary output, vital signs, and giving fluid Intravenous if necessary.

Label The oral

LD50 in rats is 3576.2 mg/kg.

The FDA has classified methocarbamol as pregnancy category C. Label Animal and human studies have not been performed to determine the risks to a fetus, however fetal and congenital abnormalities have been reported.

Methocarbamol is excreted in the milk of dogs, however it is unknown if this is also the case for humans.

Caution should be exercised when taking methocarbamol while breastfeeding.

Studies to assess the carcinogenicity, mutagenicity, or effects on fertility of methocarbamol have not been performed.

Since methocarbamol may possess a general

CNS depressant effect, patients receiving Methocarbamol tablets, USP should be cautioned about combined effects with alcohol and other CNS depressants.

Safe use of

Methocarbamol tablets, USP has not been established with regard to possible adverse effects upon fetal development.

There have been reports of fetal and congenital abnormalities following in utero exposure to methocarbamol.

Therefore, Methocarbamol tablets, USP should not be used in women who are or may become pregnant and particularly during early pregnancy unless in the judgment of the physician the potential benefits outweigh the possible hazards.

Methocarbamol may impair mental and/or physical abilities required for performance of hazardous tasks, such as operating machinery or driving a motor vehicle.

Patients should be cautioned about operating machinery, including automobiles, until they are reasonably certain that methocarbamol therapy does not adversely affect their ability to engage in such activities.

Methocarbamol tablets, USP are contraindicated in patients hypersensitive to methocarbamol or to any of the tablet components.

Methocarbamol tablets, USP, 500 mg – Adults: Initial dosage: 3 tablets q.i.d.

Maintenance dosage: 2 tablets q.i.d.

Methocarbamol tablets, USP: 750 mg – Adults: Initial dosage: 2 tablets q.i.d.

Maintenance dosage: 1 tablet q.4h. or 2 tablets t.i.d.

Six grams a day are recommended for the first to 72 hours of treatment. (For severe conditions 8 grams a day may be administered).

Thereafter, the dosage can usually be reduced to approximately 4 grams a day.

Methocarbamol tablets, USP 750 mg tablets are modified capsule shape, white to off-white tablet, debossed S on one side and plain on the reverse side.

They are supplied as follows

Bottles of 30 NDC 63187-130-30 Bottles of 40 NDC 63187-130-40 Bottles of 45 NDC 63187-130-45 Bottles of 60 NDC 63187-130-60 Bottles of 90 NDC 63187-130-90 Store at controlled room temperature, between 20°C and 25°C (68°F and 77°F). .

Dispense in tight container.

Store at controlled room temperature, between 20°C and 25°C (68°F and 77°F). .

Dispense in tight container.

Teratogenic effects Pregnancy Category C

Animal reproduction studies have not been conducted with methocarbamol.

It is also not known whether methocarbamol can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity.

Methocarbamol tablets, USP should be given to a pregnant woman only if clearly needed.

Safe use of

Methocarbamol tablets, USP has not been established with regard to possible adverse effects upon fetal development.

There have been reports of fetal and congenital abnormalities following in utero exposure to methocarbamol.

Therefore, Methocarbamol tablets, USP should not be used in women who are or may become pregnant and particularly during early pregnancy unless in the judgment of the physician the potential benefits outweigh the possible hazards See Warnings.

Nursing mothers

Methocarbamol and/or its metabolites are excreted in the milk of dogs; however, it is not known whether methocarbamol or its metabolites are excreted in human milk.

Because many drugs are excreted in human milk, caution should be exercised when Methocarbamol tablets, USP are administered to a nursing woman.

Pediatric use Safety and effectiveness of

Methocarbamol tablets, USP in pediatric patients below the age of 16 have not been established.

Methocarbamol and/or its metabolites are excreted in the milk of dogs; however, it is not known whether methocarbamol or its metabolites are excreted in human milk.

Because many drugs are excreted in human milk, caution should be exercised when Methocarbamol tablets, USP are administered to a nursing woman.

Safety and effectiveness of

Methocarbamol tablets, USP in pediatric patients below the age of 16 have not been established.