Methocarbamol Side Effects: What to Expect and When to Call Your Doctor

Like all medications, Methocarbamol (Robaxin) can cause side effects. The good news is that most side effects are mild and manageable, and the drug is generally well-tolerated for its intended short-term use. Here's what you need to know — from what's common and expected, to the serious symptoms that warrant a call to your doctor or a trip to the ER.

Common Side Effects of Methocarbamol

These side effects are frequently reported and are generally not cause for concern unless they are severe or don't improve:

Drowsiness / sedation: The most commonly reported side effect. Methocarbamol is a CNS depressant, so some degree of sleepiness is expected, especially in the first few days.

Dizziness or lightheadedness: Often related to the CNS-depressant effect; most common when first starting the medication or standing up quickly.

Headache: Reported by some patients, usually mild.

Nausea / upset stomach: Taking Methocarbamol with food can help reduce stomach discomfort.

Metallic taste: Some patients report an unusual taste in the mouth, especially with the injectable form.

Blurred vision: Can occur, usually temporary. Avoid driving until you know how the medication affects your vision.

Confusion / difficulty concentrating: Mild cognitive effects are possible, particularly in older adults. Discuss with your doctor if significant.

Nasal congestion: Stuffy nose has been reported, particularly with the injectable form.

What Are Normal vs. Concerning Symptoms?

Feeling mildly tired or a little dizzy on the first day or two of Methocarbamol is normal, especially if you take it on an empty stomach. The sedation effect often improves as your body adjusts, and it's also reduced because most prescriptions are only for a few days.

However, if you experience extreme drowsiness, trouble staying awake, or feel significantly "off" in a way that concerns you, contact your doctor or pharmacist right away.

Serious Side Effects: When to Seek Immediate Help

Stop taking Methocarbamol and seek emergency medical care or call 911 immediately if you experience:

Signs of allergic reaction: Hives, rash, difficulty breathing, swelling of face/lips/tongue/throat (anaphylaxis)

Seizures: Rare but reported, especially with IV administration in patients with epilepsy

Fainting / syncope: Loss of consciousness, even brief, requires medical evaluation

Signs of severe CNS depression: Slow or shallow breathing, extreme difficulty staying awake, confusion, coma

Jaundice: Yellowing of skin or eyes (cholestatic jaundice has been rarely reported)

Unusual bruising or signs of infection: Leukopenia (low white blood cell count) has been rarely reported

Important Safety Warnings

No alcohol: Do not drink alcohol while taking Methocarbamol. Alcohol significantly amplifies CNS depression and increases the risk of dangerous sedation.

Driving and machinery: Do not drive or operate machinery until you know how Methocarbamol affects you. Even if you feel fine, reaction times may be impaired.

Opioids, benzodiazepines, sleep aids: Using these alongside Methocarbamol can cause profound sedation, respiratory depression, coma, and death. Tell your doctor about ALL medications you're taking.

Older adults: Adults 65+ are at increased risk of falls and cognitive side effects. Methocarbamol is on the Beers Criteria list of potentially inappropriate medications for older adults.

Does Methocarbamol Cause Addiction or Dependence?

Unlike carisoprodol (Soma), which is a Schedule IV controlled substance, Methocarbamol is not federally scheduled. Research on its abuse potential has produced mixed results — some studies show mild abuse potential at high doses, while others show little. The product label does not carry a formal warning about abuse, addiction, or dependence. For the typical short-term use prescribed for acute muscle pain, dependence is not a significant clinical concern.

Methocarbamol and Lab Tests

An important and often overlooked side effect: Methocarbamol can cause false results in certain urine screening tests. Specifically, it may interfere with tests for 5-HIAA (a marker for carcinoid tumors) and vanillylmandelic acid (VMA). If you are scheduled for any urine tests, tell your healthcare provider and the lab that you are taking Methocarbamol.

For a comprehensive list of drug interactions, see our guide: Methocarbamol Drug Interactions: What to Avoid and What to Tell Your Doctor.

If you're struggling to find Methocarbamol at your pharmacy, medfinder can help you locate which pharmacies near you have it in stock.