Methocarbamol - Uses and Mechanism of Action

Overview:

Methocarbamol is available in generic and brand name Robaxin and comes in the form of tablets, capsules, and injections. The drug is available as an over-the-counter muscle relaxant and is prescribed alongside rest, exercise, and physical therapy for best results. Methocarbamol helps relieve pain from injury, fractures, and tetanus by blocking the nerve impulses of pain in the brain.

Methocarbamol is used for relieving involuntary non-specific muscle spasms. Methocarbamol shows fewer sedative effects than opioids. The drug is suitable to be administered during the day for patients with acute or chronic muscle pain. The oral drug is also available at a lower dose in combination with Acetaminophen or Ibuprofen. The most common side effect is drowsiness, blurred vision, and headache.

Drug Group:

Methocarbamol belongs to the class of skeletal muscle relaxants. These drugs block and slow down the activities in the nervous system of the body. This further relaxes the muscles and gives relief from pain.

Muscle relaxants can be classified into two categories:

Antispasticity Medications - They relieve or prevent spasms related to pain and limited function to perform daily activities.

Antispasmodic Medications - They directly affect the spinal cord or the skeletal muscles, improve muscle tightness and reduce musculoskeletal pain and spasms. Methocarbamol is an antispasmodic medication.The other skeletal muscle relaxants with antispasmodic effects are Cyclobenzaprine and Carisoprodol.

What Is Methocarbamol Used For?

1. Methocarbamol is used to manage discomfort associated with painful contractions of muscles caused by muscle injury and sprains. The drug releases muscle tension and is prescribed in cases of spinal cord injury and severe postoperative orthopedic surgeries.

2. The drug reduces involuntary muscle stiffness by relaxing the muscles to relieve discomfort. These drugs improve the hypertonicity and uncontrolled and involuntary activity of the muscles.

3. The drug relieves the pain associated with lockjaw (tightening of the jaw and neck muscles) and alters the transmission of sensations of CNS conduction.

4. Methocarbamol is indicated as an adjunct to physical therapy and rest for the relief of acute, painful musculoskeletal conditions.

How Does Methocarbamol Work?

Methocarbamol is a drug that acts on the central nervous system and relaxes the muscles. They are mainly indicated in the treatment of acute musculoskeletal pain. It inhibits neural conduction activities in the central nervous system. The drug reduces muscle spasms and has a less sedative effect. It decreases the transmission in spinal pathways and blocks the spinal polysynaptic reflexes.

What Is the Onset of Action of Methocarbamol?

What Is the Onset of Action of Methocarbamol?

The drug is mostly administered orally and is available in 500 and 750 mg tablets. The drug takes 30 minutes to be absorbed and reaches the maximum concentration in the gastrointestinal tract. It reaches its peak concentration in plasma in two hours, and plasma protein binding is 46 % to 50 % in healthy people. Methocarbamol is broken down in the liver and nearly all are excreted as an inactive metabolite in the urine within four hours of taking the drug. Only 2 % of the absorbed drug remains in the blood after the last dose is taken.

The metabolism of Methocarbamol is influenced by patient's age and the health of their kidneys and liver. The drug is utilized better in younger patients as compared to older patients and has a poor rate of effectiveness in people with pre-existing medical conditions.

Habit-Forming:

Methocarbamol can be addictive for some people, especially when taken without a prescription and in people with a history of drug abuse.

Expiry Date:

Avoid taking medicines after their expiry date. The expiry date is printed on the back of the medicine pack.

What Is the Dosage of Methocarbamol?

The oral route commonly administers Methocarbamol. It is available in 500 mg and 750 mg oral tablets.

Oral Dose for Muscle Spasm in Adults-

The drug should not be given for more than three consecutive days. This is followed with an interval of 48 hours and may be repeated if a condition persists.

Dosage for Tetanus:

Methocarbamol controls the neuromuscular signs of tetanus. A total of 30 ml is injected as an initial dose. This is repeated every six hours till the conditions subside.

Dosage for Pediatric Patients:

An initial dose of 15 mg/kg injection is recommended four times a day.

The total dose should not exceed 1.8 g for three consecutive days.

How to Use Methocarbamol?

The medicine is available in the form of tablets and injections. It is taken with or without food as directed by the doctor. Taking the medicine after food prevents stomach upset. The dose should not be increased or decreased without instruction by the doctor. Take medicine at the time recommended by the doctor and not for longer than the prescribed duration. Inform the doctor if there is no change or worsening of the condition.

Missed Dose:

In case you miss a dose of Methocarbamol, you may take it as soon as you remember. Do not take two tablets together as it can cause adverse reactions. If it's almost time for the next dose, skip the missed dose and take the next dosage.

What Are the Drug Warnings and Precautions?

Always inform your doctor if you have any of the following conditions:

• Pregnancy and Breastfeeding Women - The medicines should be taken only if advised. The doctor will discuss the risks and benefits.

• Activities Requiring Mental Alertness - The patient is cautioned of impaired mental and physical activities required in driving and operating machinery. Therefore, do not involve yourself in activities that require attention after taking this drug.

• Renal Impairment - Intravenous dose should be used with caution in people with mild to moderate kidney conditions. For patients on dialysis, it should be used with precautions.

• Hepatic Impairment - As the drug is metabolized mainly in the liver, inform the doctor about the liver condition.

• Pediatrics - The safety of the drug is not confirmed in children below the age of 16 and so take the medication only after consulting with the doctor.

• Drug Hypersensitivity - It is contraindicated in people with a history of hypersensitivity to Methocarbamol.

• Abuse - Inform the doctor of the previous history of drug misuse.

• Myasthenia Gravis - Methocarbamol is contraindicated in patients with myasthenia gravis as it can exaggerate muscle weakness and fatigue.

• Geriatrics - The medicines should be avoided in adults older than 65, as they can increase the risk of injury, fracture, and fall.

What Are the Side Effects of Methocarbamol?

The common side effects of Methocarbamol are

• Headaches.

• Dizziness.

• Lightheadedness.

• Drowsiness.

• Sedation.

These are mild effects and may go away in a few days.

Serious side effects may include;

• Slow heart rate.

• Flushing.

• Allergic reactions with symptoms like rash, itching, hives, swelling of the face, chest tightness, and difficulty in breathing.

• Low blood pressure.

• Low white blood cells.

• Confusion.

• Blurred vision.

• Seizures.

• Vertigo.

• Angioneurotic edema with symptoms like swelling of the voice box and swollen tissues.

Call the doctor immediately if you have any of these symptoms.

What Are the Interactions of Methocarbamol?

Methocarbamol can interact with other medicines, food, or vitamins and this can make the drug less effective or may increase the side effects.

With Other Medicines-

• Pyridostigmine bromide

• Lorazepam

• Diazepam

• Tramadol

• Clonazepam

• Amitriptyline

• Doxepin

• Morphine

• Chlorpromazine

• Haloperidol

• Quetiapine

• Imipramine

• Hydrocodone

• Alprazolam

With Alcohol-

Consuming alcohol with Methocarbamol depresses the central nervous system and slows brain activity heart rate and breathing.

With Food and Herbal Products-

• Valerian Root - Taking these with Methocarbamol increases side effects like dizziness, confusion, and drowsiness.

• Kava-Kava - When kava-kava is taken with Methocarbamol, it increases the side effects like sedation

With Diseases-

The drug tends to build up in the body of patients with liver and kidney diseases and is not metabolized. Therefore, it should be used cautiously in patients with liver and renal problems.

What Are the Common Trade Names of Methocarbamol?

1. Tablet Methoriv 500 mg.
2. Tablet Flexpsule Robaxin 750 mg.
3. Tablet Mylax 500 mg.
4. Tablet Robinax 500 mg.
5. Tablet Robaxisal.
6. Tablet Neuroma.
7. Tablet Robiflaminol 500 mg.
8. Tablet Methopar 500 mg.
9. Tablet Asolt-AT.
10. Tablet Apadik 500 mg.