Label: METHOCARBAMOL injection

Methocarbamol injection, USP, a carbamate derivative of guaifenesin, is a central nervous system (CNS) depressant with sedative and musculoskeletal relaxant properties. It is a sterile, pyrogen-free solution intended for intramuscular or intravenous administration.

Each mL contains: methocarbamol, USP 100 mg, polyethylene glycol 300, NF 0.5 mL, Water for Injection, USP q.s. The pH is adjusted, when necessary, with hydrochloric acid and/or sodium hydroxide. The chemical name of methocarbamol is 3‑(2‑methoxyphenoxy)‑1,2-propanediol 1‑carbamate and has the empirical formula of C 11H 15NO 5. Its molecular weight is 241.24. The structural formula is shown below:

Methocarbamol is a white powder, sparingly soluble in water and chloroform, soluble in alcohol (only with heating) and propylene glycol, and insoluble in benzene and n‑hexane.

Methocarbamol Injection has a pH between 3.5 and 6.0.

AFTER MIXING WITH I.V. INFUSION FLUIDS, DO NOT REFRIGERATE.

The mechanism of action of methocarbamol in humans has not been established, but may be due to general CNS depression. It has no direct action on the contractile mechanism of striated muscle, the motor end plate or the nerve fiber.

The injectable form of methocarbamol is indicated as an adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute, painful musculoskeletal conditions. The mode of action of this drug has not been clearly identified, but may be related to its sedative properties. Methocarbamol does not directly relax tense skeletal muscles in man.

Methocarbamol Injection should not be administered to patients with known or suspected renal pathology. This caution is necessary because of the presence of polyethylene glycol 300 in the vehicle.

A much larger amount of polyethylene glycol 300 than is present in recommended doses of Methocarbamol Injection is known to have increased pre-existing acidosis and urea retention in patients with renal impairment. Although the amount present in this preparation is well within the limits of safety, caution dictates this contraindication.

Methocarbamol Injection is contraindicated in patients hypersensitive to methocarbamol or to any of the injection components.

Since methocarbamol may possess a general CNS depressant effect, patients receiving Methocarbamol Injection should be cautioned about combined effects with alcohol and other CNS depressants.

Safe use of Methocarbamol Injection has not been established with regard to possible adverse effects upon fetal development. There have been very rare reports of fetal and congenital abnormalities following in utero exposure to methocarbamol. Therefore, Methocarbamol Injection 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 PRECAUTIONS: Pregnancy).

The following adverse reactions have been reported coincident with the administration of methocarbamol. Some events may have been due to an overly rapid rate of intravenous injection.

Body as a whole:Anaphylactic reaction, angioneurotic edema, fever, headache

Cardiovascular system:Bradycardia, flushing, hypotension, syncope, thrombophlebitis

In most cases of syncope there was spontaneous recovery. In others, epinephrine, injectable steroids, and/or injectable antihistamines were employed to hasten recovery.

Digestive system:Dyspepsia, jaundice (including cholestatic jaundice), nausea and vomiting

Hemic and lymphatic system:Leukopenia

Immune system:Hypersensitivity reactions

Nervous system:Amnesia, confusion, diplopia, dizziness or light-headedness, drowsiness, insomnia, mild muscular incoordination, nystagmus, sedation, seizures (including grand mal), vertigo

The onset of convulsive seizures during intravenous administration of methocarbamol has been reported in patients with seizure disorders. The psychic trauma of the procedure may have been a contributing factor. Although several observers have reported success in terminating epileptiform seizures with Methocarbamol Injection, its administration to patients with epilepsy is not recommended (see PRECAUTIONS: General).

Skin and special senses:Blurred vision, conjunctivitis, nasal congestion, metallic taste, pruritus, rash, urticaria

Other:Pain and sloughing at the site of injection

Limited information is available on the acute toxicity of methocarbamol. Overdose of methocarbamol is frequently in conjunction with alcohol or other CNS depressants and includes the following symptoms: nausea, drowsiness, blurred vision, hypotension, seizures, and coma. In post-marketing experience deaths have been reported with an overdose of methocarbamol alone or in the presence of other CNS depressants, alcohol or psychotropic drugs.

For Intravenous and Intramuscular Use Only.Total adult dosage should not exceed 30 mL (3 vials) a day for more than 3 consecutive days except in the treatment of tetanus. If the condition persists, a like course may be repeated after a drug-free interval of 48 hours. Dosage and frequency of injection should be based on the severity of the condition being treated and therapeutic response noted.

For the relief of symptoms of moderate degree, one dose of 1 gram (one 10 mL vial) may be adequate. Ordinarily this injection need not be repeated, as the administration of the oral form will usually sustain the relief initiated by the injection. For the severest cases or in postoperative conditions in which oral administration is not feasible, additional doses of 1 gram may be repeated every 8 hours up to a maximum of 3 g/day for no more than 3 consecutive days.

Methocarbamol Injection, USP, (100 mg/mL) is supplied in 10 mL single-dose vials (NDC 70436-149-33), in cartons of 25 vials (NDC 70436-149-55).

Store at 20° to 25°C (68° to 77°F); excursions permitted to 15° to 30°C (59° to 86°F). [See USP Controlled Room Temperature.]

Not made with natural rubber latex.

To report SUSPECTED ADVERSE REACTIONS, contact Slate Run Pharmaceuticals, LLC. at 1-888-341-9214 or the FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Manufactured by:

Hainan Poly Pharm. Co., Ltd., Guilinyang Economic Development Zone, Haikou, Hainan, China 571127

Distributed by:

Slate Run Pharmaceuticals, LLC, Columbus, Ohio 43215

10000443/01

Revised: 09/2023

Methocarbamol Injection, USP, 1,000 mg/10 mL (100 mg/mL), 10 mL Single-Dose Vial

NDC 70436-149-33