Dry mouth, Drowsiness, and Dizziness: 11 Tizanidine Side Effects You Should Know About
Key takeaways:
Tizanidine (Zanaflex) is a muscle relaxant that treats muscle spasms. Common side effects include dry mouth (xerostomia), tiredness, and low energy. Dizziness, low blood pressure, and constipation are also possible.
Rare but serious tizanidine side effects include liver damage and hallucinations.
If you want to stop taking tizanidine, talk to your prescriber before making any changes. They’ll help you slowly lower your dosage to avoid withdrawal symptoms.
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Table of contents
Tizanidine (Zanaflex) is an FDA-approved medication that treats tight, stiff muscles (also known as muscle spasticity). It’s part of a group of medications called muscle relaxers.
As with all medications, tizanidine may have side effects. So it’s important to know what to watch out for while you’re taking this medication.
Tizanidine side effects at a glance
Some tizanidine side effects can be managed at home and may go away on their own as your body gets used to the medication. Common tizanidine side effects include:
Dry mouth
Tiredness
Feeling weak or lacking energy
Dizziness
Common cold symptoms, such as sore throat and runny nose
Constipation
Nausea and vomiting
Urinary tract infection (UTI)
Low blood pressure (hypotension)
Low heart rate (bradycardia)
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Even though they’re rare, more serious tizanidine side effects are also possible. These may require you to reach out to your healthcare team. Or you may need emergency care. These severe side effects include:
Extremely low blood pressure and heart rate
Extreme drowsiness, especially when taken with certain medications such as opioids or benzodiazepines
Liver damage
Hallucinations
Tizanidine withdrawal
Below, we’ll take a closer look at 11 notable tizanidine side effects and how to manage them.
1. Dry mouth
Dry mouth, also called xerostomia, is the most common tizanidine side effect. This can be uncomfortable and make it difficult to chew or swallow.
You can do a few things to help relieve a dry mouth, such as:
Stay hydrated. Keeping your mouth moist may help improve dry mouth. Drinking plain water is a good option, but you can also drink unsweetened beverages or flavor your water. Sucking on ice chips might also provide relief.
Chew sugar-free gum with xylitol. Sugar-free gum with xylitol may help you make more saliva, which can help relieve dry mouth. If you can’t chew gum, sugar-free hard candy may have the same effect.
Try saliva substitutes. Saliva substitutes are available over the counter (OTC), including Biotene and BioXtra. They come in many forms including lozenges, sprays, and liquids. You might need to try a few different products before you find the one that works best for you.
These tips can help you avoid the discomfort of dry mouth and maintain good oral hygiene. Dry mouth may lead to tooth decay and infection. A good dental care routine can help prevent these problems, too. Make sure to brush your teeth twice a day, floss every day, and see your dentist regularly.
If dry mouth continues to be an issue or feels severe, let your prescriber know. They may lower your tizanidine dose or suggest a different treatment.
2. Tiredness
Many people who take tizanidine experience tiredness as a side effect. In fact, it’s one of the most common tizanidine side effects. If you only take tizanidine close to bedtime, this may not be a problem. But if you take tizanidine a few times a day, drowsiness can affect your ability to complete your daily tasks.
What drug interactions can occur with tizanidine? Find out which medications affect how long tizanidine stays in your body and can increase side effects.
How do you take tizanidine? Learn about which dosage of tizanidine is right for you.
How long does tizanidine last in the body? Tizanidine effects last about 3 to 6 hours after you take it, though the medication can stay in your body longer.
Daytime sleepiness may be bothersome, and even dangerous. Avoid tasks that require alertness, like driving, when you’re first starting tizanidine. Once you see how tizanidine affects you, you’ll know whether you can safely resume these activities.
If you’re constantly tired throughout the day, let your healthcare team know. They can help determine if tizanidine is the cause. You may need a lower dose, a different dosing schedule, or a different muscle relaxer altogether. A muscle relaxer that’s less likely to cause drowsiness, such as methocarbamol, might be an option for you.
Pharmacist Tip: Taking tizanidine with other substances that can also cause drowsiness may be dangerous. These include opioids, benzodiazepines, and alcohol. It even includes OTC products like diphenhydramine (Benadryl). It’s best to avoid tizanidine with these substances. But sometimes this isn’t possible. For example, some people may need an opioid and muscle relaxer to manage pain. If this is your situation, discuss the risks with your prescriber.
3. Low energy
Taking tizanidine may cause weakness and low energy. Like dry mouth and drowsiness, it’s one of the most common tizanidine side effects. Let your healthcare team know if you regularly feel low on energy for days or weeks after starting tizanidine.
A few things can help keep your energy levels high. For example, nutrient-rich, whole foods are known to boost energy levels. These include berries, leafy green vegetables, and whole grains. Lowering stress levels, exercising regularly, and taking a 15- to 20-minute nap between noon to 2PM can also help.
Keep in mind: There are many possible reasons for feeling a lack of energy, including low-quality sleep or anxiety. So, if you feel constantly fatigued, something else may be going on besides tizanidine. Your healthcare team can help you figure out why you are feeling this way.
4. Dizziness
Tizanidine may cause dizziness. This can occur with or without low blood pressure (more on that below).
If you feel dizzy, be careful when changing positions (like going from sitting to standing). Also, consider having something sturdy to hold on to when you’re standing up.
Sometimes, dizziness improves on its own. But If you have other symptoms that come with dizziness, such as a high fever, severe headache or neck pain, or seizures, seek medical attention immediately. These are signs that something more serious is going on.
Similar to drowsiness, dizziness from tizanidine may be worse if you take it with other medications that cause the same effect. These include opioids, blood pressure medications, and some antidepressants.
5. Low blood pressure
Low blood pressure, also known as hypotension, is another possible tizanidine side effect. Symptoms of hypotension include blurry vision, weakness, and feeling lightheaded or dizzy. Hypotension is more likely if you take other medications that lower blood pressure, including various blood pressure and heart medications. Examples include angiotensin-converting enzyme (ACE) inhibitors, beta blockers, and diuretics.
If you take tizanidine and blood-pressure-lowering medications, your prescriber may recommend checking your blood pressure at home. If it’s lower than your target blood pressure goal, and you have symptoms of low blood pressure, call 911. You may need emergency care. If tizanidine is the cause, you’ll need a lower tizanidine dose or to switch to another medication.
6. Constipation
Constipation is another possible tizanidine side effect. Typically, constipation from tizanidine will be mild and resolve on its own or can be managed at home. Tips for preventing and managing constipation at home include:
Drinking enough fluids
Eating plenty of fiber
Exercising regularly
Try having a bowel movement near the same time each day.
Try an OTC laxative. Your prescriber can help you choose a good option, such as polyethylene glycol (Miralax) or a stool softener like docusate (Colace, DocQlace).
If your constipation is severe, you may need medical attention. If you have symptoms such as rectal bleeding, intense abdominal pain, or vomiting from constipation, get help right away.
7. Nausea or vomiting
Some people who took tizanidine in clinical trials reported vomiting. If you’re feeling nauseated while taking tizanidine, try taking it with food. This can help your stomach handle the pill a little better. Staying hydrated and eating smaller, more frequent meals throughout the day can also help.
If you have persistent nausea that leads to vomiting, talk to your healthcare team. They can help determine the cause and what to do next.
8. Cold symptoms
Symptoms of the common cold or the flu include a runny or stuffy nose, sore throat, and cough. Sneezing, body aches, and fever are also possible. Some people taking tizanidine report having some of these symptoms. However, tizanidine doesn’t actually cause the common cold or the flu.
Whether you have a cold or the flu, or just symptoms as a result of tizanidine side effects, several tips can help relieve your symptoms:
Getting adequate rest
Drinking plenty of fluids
Using a humidifier
Drinking warm tea (adding honey, ginger, and lemon may also help)
Gargling with salt water
If you have more severe symptoms — such as shortness of breath or trouble keeping down fluids — or if your symptoms last more than 3 days, it’s time to contact your healthcare team. They’ll likely want to see you in person to determine what’s going on.
9. Liver problems
It’s rare, but tizanidine can cause liver damage. In a few cases, people have died from liver damage after taking it. Your prescriber will likely check your liver function before you start tizanidine and during treatment. They’ll do this with a blood test that measures how high your liver enzymes are. They may avoid prescribing tizanidine if your test shows existing liver damage. Or they may prescribe a lower dose.
About 5% of people have a temporary increase in liver enzymes after starting tizanidine. In rare cases, more serious liver problems can occur. Symptoms of liver damage include stomach pain and swelling, dark urine, and yellowing of the skin and eyes (jaundice). If you experience any of these symptoms after starting tizanidine, let your healthcare team know immediately.
10. Hallucinations
Hallucinations are a rare but possible side effect of tizanidine. A hallucination is when you hear or see something that isn’t really there. When caused by medications, it’s called medication-induced psychosis.
Let your prescriber know if you experience hallucinations while taking tizanidine. They will likely ask you to stop taking it. Keep in mind that some people will continue to experience hallucinations for a couple of weeks, even after stopping tizanidine.
11. Withdrawal
Tizanidine is one of many medications that shouldn’t be stopped abruptly because it can cause withdrawal symptoms. Tizanidine withdrawal symptoms include:
High blood pressure
A fast heartbeat
Chest pain
Stiff muscles and difficulty moving
Tremor
Anxiety
Withdrawal symptoms are more likely if you’ve been taking high doses of tizanidine (20 mg or more daily) for about 2 months or more. It may also be more likely if you’ve been taking opioids to manage pain along with tizanidine.
To avoid withdrawal symptoms, don’t stop taking tizanidine without talking to your prescriber. They can help you come up with a plan to slowly lower your dose.
Frequently asked questions
After you take a dose of tizanidine, the medication will stay in your system for about 10 hours. This is determined by tizanidine’s half-life, or the amount of time it takes your body to remove half the medication from your system. After about five half-lives, a medication is considered to be sufficiently removed from the body.
Keep in mind that tizanidine may stick around longer in the body for some people, including older adults, who are more likely to clear medications at a slower pace.
Muscle relaxers, including tizanidine, can be riskier for older adults to take. This is because the drowsiness and dizziness caused by tizanidine can be more dangerous in older adults, who are more likely to have injury and disability from falls. Older adults are also more likely to have kidney and liver problems, which also increases the risk of tizanidine side effects.
If you're over 65 years old and your prescriber recommends tizanidine, they may recommend a lower dose than what’s typically used.
Yes, it’s possible to die from taking too much tizanidine. However, accidentally taking an extra dose or two isn’t likely to cause serious effects. People who take large amounts of tizanidine may experience extremely low blood pressure, slowed heart rate, and confusion. In severe cases, this may lead to coma and death.
Anyone who takes a large amount of tizanidine should get medical help right away by calling Poison Control at 1-800-222-1222 or going to the nearest emergency room.
Tizanidine isn’t known to cause diarrhea. It’s more likely to cause constipation. If you have diarrhea while taking tizanidine, there’s likely a different cause.
The bottom line
Tizanidine (Zanaflex) is a muscle relaxant that treats stiff, tight muscles. Common tizanidine side effects include dry mouth (xerostomia), tiredness, and dizziness. Rare but more serious side effects include liver damage and hallucinations.
Some tizanidine side effects may be managed at home. However, more serious side effects require a call to your healthcare team right away. Regardless, if you’re experiencing side effects that don’t improve or feel severe, let your prescriber know. They can help you decide what to do next. This may involve lowering your dose, stopping your tizanidine, or switching to another medication.
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References
Advanced Rx of Tennessee, LLC. (2024). Tizanidine- tizanidine tablet [package insert].
National Institute of Diabetes and Digestive and Kidney Diseases. (2017). Tizanidine. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury.
Talha, B., et al. (2023). Xerostomia. StatPearls.
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