8 Muscle Relaxer Side Effects: Drowsiness, Dry Mouth, and More
Key takeaways:
Muscle relaxers are prescription medications used to help relieve pain and discomfort associated with muscle spasms and tension. Examples include metaxalone, carisoprodol (Soma), and cyclobenzaprine (Amrix).
Many muscle relaxers share common side effects, including drowsiness, dizziness, and fatigue. Your healthcare team can work with you to find the right dosage to minimize most side effects.
Some people can be at a higher risk for muscle relaxer side effects, such as older adults. Other medications can also worsen muscle relaxer side effects when they’re taken together.
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Table of contents
If you’ve been dealing with relentless muscle tension, even the simplest tasks can feel like an uphill battle. Muscle relaxers, such as metaxalone and cyclobenzaprine (Amrix), can be an option for relief. But there’s a catch — they often make people feel drowsy, dizzy, and fatigued.
With muscle relaxers, it comes down to striking the right balance between finding comfort and managing side effects. And while specific muscle relaxer side effects can vary between medications, there are some side effects that are possible with all or most of them. We review eight common muscle relaxer side effects below.
1. Drowsiness
One common muscle relaxer side effect is drowsiness. This is because most of them have a sedative effect on your central nervous system (brain and spinal cord). But some muscle relaxers may be more sedating than others. And in general, the severity of drowsiness can also depend on your dose.
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There aren’t studies comparing drowsiness between different muscle relaxers. But there’s some evidence suggesting that metaxalone and methocarbamol may be less sedating than other types. More research is needed to know for sure. And since everyone responds to medications differently, there’s no telling before taking them how each one will affect you.
Certain formulations of the same medication may also have different risks of drowsiness. For example, drowsiness appears to happen less often with extended-release (ER) cyclobenzaprine compared with the immediate-release (IR) form.
If your muscle spasms are interfering with a good night’s sleep, your prescriber may recommend a more sedating option that can help you sleep better at night. Or, they may suggest taking your dose in the evening if drowsiness is affecting your daytime activities.
When starting a muscle relaxer, see how it makes you feel before driving or performing other activities that require you to be alert. Tell your prescriber if your drowsiness is severe or interfering with your daily functioning. They may be able to lower your dose or help you choose a different treatment option.
2. Dizziness
Dizziness is another common muscle relaxer side effect. This can put you at risk for falls, which are especially dangerous if you’re an older adult. For this reason, as well as the risk of drowsiness and other possible side effects, experts strongly recommend avoiding muscle relaxers if you’re 65 or older.
If you feel dizzy, sit or lie down until you feel more stable on your feet. After the feeling passes, rise slowly, making sure that you have something to hold onto. Call someone for help if you don’t think you’re able to get up safely on your own.
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There are many other things that can put you at risk for dizziness. So, it may help to try some of these preventive measures:
Stay well-hydrated throughout the day to prevent dehydration.
Monitor your blood pressure and blood glucose (sugar), if applicable to you.
Review your medication list with your healthcare team for potential interactions.
3. Dry mouth
Dry mouth can be a side effect of muscle relaxers that have anticholinergic effects. This means they block the action of acetylcholine, a chemical involved in muscle contractions, secretions, and other body functions. Cyclobenzaprine, tizanidine (Zanaflex), and orphenadrine are three notable examples.
Most of the time, dry mouth can be managed at home. If it happens to you, here are a few tips for relief:
Chew gum to boost saliva production.
Suck (don’t chew) on ice chips.
Take small sips of water throughout the day.
Check out saliva substitutes available over the counter (OTC).
Avoid or limit foods and drinks that can worsen dry mouth, such as salty or acidic foods.
If these tips aren’t helping, reach out to your prescriber for additional dry mouth management advice.
4. Headache
Headache is another possible side effect of taking a muscle relaxer. For example, headaches have been reported with orphenadrine, metaxalone, and carisoprodol. However, there are also some muscle relaxers, such as tizanidine, that are sometimes prescribed off-label to prevent chronic headaches or migraines.
If you get headaches during treatment for muscle spasm or tension, they may lessen as your body gets used to the medication. And in the meantime, there are ways to get relief at home. For example, OTC treatments such as acetaminophen (Tylenol) may help.
But if your headaches are persistent, talk to your prescriber. They can help you tease out what may be causing your headaches, which may be your muscle relaxer or something else.
5. Fatigue
Muscle relaxers slow down your central nervous system. So, you might feel more tired, lack energy, or have difficulty concentrating while taking them. As with other side effects, see how you respond to the medication before performing tasks that require you to be alert or focused.
Talk to your prescriber if your fatigue is interfering with your daily activities. If it’s an option, they may suggest taking your muscle relaxer dose in the evening to see if that helps lessen fatigue during the day. If needed, they may lower your dose or switch you to a different formulation of your medication (if available) or a different type of muscle relaxer.
6. Nausea
Muscle relaxers can sometimes cause you to feel nauseous. Oftentimes, they can be taken with or without food. If taking your dose on an empty stomach makes you nauseous, try taking it with a meal or snack. Your pharmacist can tell you if this is an option for your medication.
Other ways to help manage nausea include avoiding spicy or greasy foods, which can trigger nausea, and drinking plenty of water. Eating smaller meals throughout the day can also help. You can also consider giving ginger or acupressure a try. And if it’s an option for you, changing your dose time to bedtime may be beneficial.
7. Constipation
If you’ve noticed a change in your bowel movements after starting a muscle relaxer, it could be due to your medication. Similar to dry mouth, constipation is another anticholinergic side effect of certain muscle relaxers, including cyclobenzaprine and baclofen.
You can help counter constipation by following these tips:
Get plenty of exercise: Some studies have shown that physical movement can have a positive effect on constipation.
Add fiber to your diet: Certain types of fiber pull water into your stool and can help it move out of your system.
Try an OTC laxative: If lifestyle changes aren’t helping, your pharmacist can recommend a laxative that’s best for your situation.
It’s also possible that other medications you’re taking may be causing or worsening constipation. Your healthcare team can review your current medication list to find potential culprits. These can include prescription and OTC medications.
8. Blurry vision
Less commonly, muscle relaxers can cause or contribute to blurry vision. This is another potential anticholinergic side effect that can happen from the medication drying out your eyes. In this case, there are many OTC and home dry eye remedies you can try.
If dry eye treatments aren’t helping, contact your prescriber. They may adjust your dosage or have you try a different medication.
When should you contact your prescriber about muscle relaxer side effects?
Contact your prescriber if you experience any side effects that are bothersome or don’t seem to be getting better with time. In some cases, they may lower your dose or have you change how or when you’re taking the medication.
More serious side effects from taking muscle relaxers are possible, but they’re much less common. Get medical help right away if you experience any of these symptoms:
Anaphylaxis symptoms, such as trouble breathing, hives, and swelling in your face or throat
Seizures
Abnormal heart rhythm
Serotonin syndrome symptoms, including sweating, shakiness (tremors), and confusion
The bottom line
Common muscle relaxer side effects include drowsiness, dizziness, and fatigue. Headache, dry mouth, and blurry vision are also possible. These side effects may affect older adults more significantly, which is why muscle relaxers aren’t recommended for people 65 or older.
Many of these side effects can be managed at home. But if they become bothersome, your prescriber can evaluate your dosage and may even recommend a different treatment option.
Serious side effects, such as seizures and an abnormal heart rhythm, aren’t common. Be sure to discuss all possible side effects of your muscle relaxer with your prescriber and know when to seek immediate medical attention.
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References
2023 American Geriatrics Society Beers Criteria Update Expert Panel. American Geriatrics Society 2023 updated AGS Beers Criteria for potentially inappropriate medication use in older adults. Journal of the American Geriatrics Society.
See, S., et al. (2008). Choosing a skeletal muscle relaxant. American Academy of Family Physicians.
Weil, A. J. (2009). Cyclobenzaprine extended release for acute low back and neck pain. Therapy.
