What Are the Most Common Methocarbamol Side Effects?

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  • Written By: R. Britton
  • Edited By: R. Halprin
  • Last Modified Date: 20 July 2019
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Methocarbamol is an antispasmodic or muscle relaxing drug most commonly available in oral form. This drug is used to relieve pain and muscular spasms caused by a variety of conditions and sports-related injuries. Similar to most medications, it carries a risk of adverse reactions ranging from a mild headache to a life-threatening allergy. There are also a number of contraindications with this medication.

This muscle relaxant is usually prescribed as an oral tablet but is also available as an injection. It is often used to treat pain and prevent spasms in muscloskeletal injuries. Methocarbamol does not work directly on the muscles but instead inhibits or interrupts the signals sent to the brain via the nerves to prevent the muscles from going into spasm.

The most common and mild temporary methocarbamol side effects include headaches, lethargy, diarrhea, constipation, and nausea. The majority of these unpleasant effects should disappear within a few days of starting treatment. If they do not clear up or if they worsen significantly, it is advisable to seek medical attention because the dosage may need alteration or the patient may need a different treatment.

Insomnia and conjunctivitis are also among the most common side effects. Increased and unexplained anxiety often occurs, particularly in patients who suffer from insomnia while taking this medication. Conjunctivitis is a bacterial eye infection sometimes called pink eye and requires treatment from a health professional.


More severe side effects include seizures and involuntary movements. It is therefore not recommended for patients who already suffer from or have a history of seizure disorders. Patients are advised to refrain from driving, operating machinery, or any other potentially hazardous task until the medication is in the system and any adverse reactions have been identified.

Methocarbamol can make patients more prone to contracting infections by weakening the immune system and lowering the white blood cell count. Severe allergic reactions have also been reported as one of the serious methocarbamol side effects. Signs of a serious reaction include difficulty breathing, swelling in the face and throat, and a red, rapidly spreading rash. If these symptoms appear, immediate medical attention is required as they could indicate a life-threatening reaction known as anaphylaxis.

There are a wide variety of contraindications associated with methocarbamol. When combined with methocarbamol, a large number of medications, herbal remedies, and diet pills can cause severe and dangerous side effects. Before beginning treatment, patients are advised to provide a full list of any supplements or other medications they are taking to avoid complications. There are also a number of health problems for which an alternative medication should be used.

Methocarbamol is not advised for people suffering from kidney problems, particularly renal failure. This is because the medication cannot be safely processed and excreted via the kidneys. Pregnant or nursing mothers should avoid this medication because it can pass easily to the baby; this medication is not intended for infants and children as methocarbamol side effects are more severe and more dangerous to youngsters.

This drug is also seldom prescribed with other antispasmodic or muscle relaxants because this combination can cause respiratory and cardiac distress. This is because the cardiothoracic muscles relax so much that they are unable to function properly. As a result, the heart struggles to beat and the muscles around the lungs cannot expand and contract effectively.


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Post 3

Methocarbamol is also given to horses who get sore from riding or who have tight muscles. It's used in small doses to help relax them and relieve minor pain. We have used it a few times for our horses and it seemed to help. At low doses, we didn't notice side effects. The vet one ordered a high dose for a horse and he did seem to be a little sedated and sleepy.

I suspect that the side effects are similar in humans and depend on the dose. Of course how long the medication is used for is important too. Short treatments at low doses will probably not cause side effects. Of course, everyone is a little different, so it's best to watch out for the side effects mentioned in the article just in case.

Post 2

@discographer-- You were lucky. Methocarbamol has given me insomnia. I just can't sleep and I have anxiety as well. If I had known that it had this many side effects, I would have avoided it in the first place. Now I'm afraid of stopping my treatment because I don't want another back spasm. I just hope the insomnia goes away soon. Otherwise, I'm going to ask my doctor to stop the treatment or switch me to something else.

Post 1

How can methocarbamol cause conjunctivitis? That's a strange side effect I had never heard of before. I suspect it's relatively rare.

The only side effect I had from methocarbamol was fatigue and lethargy. But considering that this is an antispasmodic drug, I think this is expected and normal.

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