How common are methocarbamol side effects?

In this article:

• Common side effects
• Serious side effects
• Side effects by dosage
• How soon do side effects start?
• How long do they last?
• Long-term side effects
• Warnings
• Interactions
• How to avoid side effects
• Managing side effects
• Bottom line

In this article

• Common side effects
• Serious side effects
• Side effects by dosage
• How soon do side effects start?
• How long do they last?
• Long-term side effects
• Warnings
• Interactions
• How to avoid side effects
• Managing side effects
• Bottom line

Methocarbamol is a prescription muscle relaxant. It is used to relieve muscle pain, muscle spasms, and rigidity. As a sedative, methocarbamol slows down the central nervous system, but it does not directly affect the ability of muscles to contract. Methocarbamol can be given as a tablet or an injection. Robaxin is a brand-name version of methocarbamol injection. Many side effects, like drowsiness and dizziness, are related to the sedative effects of methocarbamol. Even if not entirely avoidable, these problems can usually be managed.

Common side effects of methocarbamol

About 1 in 10 people who take methocarbamol will feel dizzy or drowsy. Other common side effects include:

• Upset stomach
• Metallic taste in the mouth
• Feeling feverish
• Hives, itching, or skin rash
• Trouble with thinking or coordination
• Headache
• Insomnia
• Double vision or blurry vision
• Stuffy nose or red eyes
• Low blood pressure

Pain, redness, or itching may occur at the injection site for people who receive an injection of methocarbamol.

Serious side effects of methocarbamol

More serious side effects of methocarbamol may include:

• Fainting and falls
• Seizures
• Slow heartbeat
• Severe allergic reactions
• Low blood counts
• Confusion and forgetfulness
• Jaundice
• Inflammation and clots in blood vessels

Methocarbamol given intravenously has been known to cause convulsive seizures in people who have a seizure disorder. Additionally, the injected drug sometimes leaks into the surrounding skin, causing redness, pain, tissue death, and skin shedding. 

Methocarbamol side effects by dosage

Some people will experience methocarbamol side effects like dizziness or sleepiness at the lowest doses. For others, side effects don’t occur until the dose is higher, if at all. Older adults may be more sensitive to side effects and at greater risk of falls and confusion. So if methocarbamol is used, it’s started at a lower dose. People who drink alcohol or take other drugs that affect the central nervous system may also experience side effects at a lower dose.

How soon do methocarbamol side effects start?

Once a tablet is swallowed, methocarbamol hits its maximum concentration in the body in about one hour. Many common side effects, especially sleepiness, dizziness, and lightheadedness, begin soon after taking the medication. A few side effects, such as seizures or jaundice, may take a few days or weeks of treatment to become a problem. People receiving methocarbamol in an IV may feel side effects right away. 

How long do methocarbamol side effects last?

Most common side effects of methocarbamol clear up when the drug is eliminated from the body. That doesn’t take long. After the last dose, it should take approximately five hours. A few effects may take longer to resolve, such as falls or injuries sustained while feeling lightheaded.

What are the long-term side effects of methocarbamol?

Methocarbamol treatment is not time-limited, though healthcare professionals usually prescribe it as a short-term treatment. There are no particular side effects associated with long-term use. 

Methocarbamol warnings

Contraindications

Methocarbamol should not be administered to individuals with a known allergy to the medicine or its inactive ingredients. Methocarbamol in IV form or as an intramuscular injection is also contraindicated in any person with lowered kidney function.

Cautions

Healthcare providers will be more cautious in using methocarbamol for : 

• Older adults, who may be at higher risk of side effects, confusion, and falls. If methocarbamol is used, it will be started at lower doses.

• Children. Methocarbamol is prescribed to children younger than 16 only as part of a treatment regimen for tetanus.

• Pregnant or breastfeeding individuals should talk with their healthcare provider about the relative risks and benefits of methocarbamol.

• • Seizure disorder. Methocarbamol given in IV form can provoke convulsive seizures in people with a history of seizures. It should also not be used as an intramuscular injection in those with seizure disorders.
  • Latex allergies. Vials of methocarbamol intended for injection have a rubber stopper. This might cause an allergic reaction during an injection. 

• People who use other CNS depressants. Methocarbamol is used with caution in those who drink alcohol or take other drugs that also slow down the central nervous system.

• People at high risk of accidents. Because methocarbamol can cause dizziness, sedation, and confusion, people who must drive or operate machinery need to know how the drug will affect them first.

Abuse and dependence

Although methocarbamol is a sedative, the FDA does not consider it to have a high risk of abuse. One study concluded that the unpleasant side effects that occur at high doses make it less likely to be misused. However, there aren’t many studies that have looked at the potential for misuse of methocarbamol. Methocarbamol does not have the same risk for dependence or withdrawal as some other muscle relaxants like benzodiazepines.

Overdose

Go to an emergency room or call a poison control center if too much methocarbamol is taken. An overdose can be fatal, especially when combined with other CNS depressants such as alcohol. If there’s any uncertainty about an overdose, look for symptoms such as:

• Nausea
• Excessive sleepiness
• Blurred vision
• Low blood pressure

A severe overdose could cause seizures and coma.

The maximum daily dose of methocarbamol should not exceed eight grams (8000 mg) per day. 

Methocarbamol interactions

While no medications are specifically prohibited, some can cause problems when taken together with methocarbamol. Combining methocarbamol with other CNS depressants will increase the sedative effects of both drugs. This can cause people to feel sleepy, less attentive, and more prone to falls and injuries. In the worst cases, people can stop breathing. CNS depressants that can cause problems with methocarbamol include:

• Other muscle relaxants
• Alcohol
• Marijuana or cannabidiols
• Benzodiazepines
• Sleeping pills
• Opioids
• Barbiturates
• Gabapentinoids
• Anxiety medications
• Antihistamines
• SSRIs
• SNRIs

This isn’t a full list of possible interactions. Tell your healthcare provider about all prescription and over-the-counter (OTC) medications you take, as well as any herbs or supplements.

How to avoid methocarbamol side effects

Methocarbamol has only a few side effects, but some of these, like sedation and nausea, are commonly experienced. Here are a few tips to minimize these problems.

1. Take methocarbamol as directed

Follow the directions given by the prescriber or written on the prescription label. Use an app or alarm to keep from missing doses, but use a checklist or app to record doses to avoid taking too many.

2. Be careful about missed doses

As with many prescription medications, a missed dose of methocarbamol can be taken when remembered. Unless, of course, it’s almost time for the next dose. Then skip the missed dose and take the next one as scheduled. This prevents taking too much medicine. 

3. Give the prescribing healthcare provider a complete medical history

Another effective way to minimize side effects is to ensure the prescriber has a comprehensive medical history. This should include health conditions, medications, dietary supplements, and herbal products. It’s especially important to mention:

• Kidney disease 
• Liver disease
• A history of seizures
• Any prescriptions for other skeletal muscle relaxants
• Any use of sedatives, barbiturates, benzodiazepines, or other CNS depressants
• Any use of Mestinon (pyridostigmine) to treat myasthenia gravis
• Any alcohol use
• Pregnancy or any plans to become pregnant
• Breastfeeding or any plans to breastfeed

4. Take methocarbamol with food

Methocarbamol can be taken on an empty stomach or with a meal or snack. If nausea and indigestion are causing problems, consider taking the methocarbamol tablets with a light snack or meal. 

5. Be careful about driving and other risky activities

The FDA advises caution for the sedative effects of methocarbamol. Potentially risky activities that require attention and responsiveness—like driving, operating machinery, or hazardous sports—should be avoided at first until the effects of the drug are known. After that, engage in these activities cautiously.

6. Remove obstacles from around the house

Driving can be risky when taking sedating drugs. But so can walking around the house. Falls and injuries are serious problems that may occur when taking medications like methocarbamol. Consider removing obstacles from well-trafficked pathways and making sure that lighting is adequate. 

7. Stop drinking alcohol

Alcohol does not mix well with methocarbamol. The combination can increase the risk of falls, injuries, and side effects. 

8. Avoid medicines and supplements that cause drowsiness

Some prescription drugs that cause sedation may be unavoidable. So be careful when taking them along with methocarbamol. However, there are over-the-counter medications that also put people to sleep and impair mental function. Antihistamines are a good example. Some dietary or herbal supplements also have sedative properties, such as melatonin, kava, and valerian. Take a break from these supplements when taking methocarbamol.

How to manage side effects

If you feel drowsy or dizzy:

• Stand up slowly
• Move carefully
• Sit or lie down if needed
• Skip risky tasks like driving or using sharp tools

If you experience nausea, vomiting, or an upset stomach, consult your healthcare provider about symptom relief options.

Seek immediate medical help if you notice signs of an allergic reaction:

• Hives
• Trouble breathing
• Swelling of the face, lips, tongue, or throat
• Drop in blood pressure
• Weak pulse

Bottom line

Methocarbamol is effective for treating muscle pain, but like all medications, it comes with side effects. Most are mild and go away quickly. Following your provider’s instructions and avoiding sedatives and alcohol will help you to stay safe while getting relief.