9 Zyvox Side Effects You Should Know About

Zyvox (linezolid) is an antibiotic used to treat bacterial infections such as pneumonia, various skin infections, and infections that are resistant to other antibiotics. Zyvox is available as an oral tablet, an oral liquid, and an injection.

Zyvox can treat many infections, but it does have some risks. Below, we’ll cover nine Zyvox side effects you should know about.

1. Diarrhea

Like any antibiotics, Zyvox can cause diarrhea. In studies, about 8% of people taking Zyvox had diarrhea. 

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Antibiotics are used to kill bad bacteria, but they can also kill the bacteria that live in your digestive tract and help with digestion. Disrupting the balance of bacteria in your gut can lead to diarrhea.

This disruption of normal gut bacteria can also lead to particularly severe diarrhea caused by a bacteria called Clostridioides difficile (C. diff). A C. diff infection can happen during, or soon after, you take antibiotics. Watery diarrhea is one of the most common signs of a C. diff infection, but it can also cause fever, stomach pain, and tiredness.

In serious cases, C. diff can cause inflammation in the intestines and blood infections. It’s also highly contagious. Before you start Zyvox, talk to your healthcare provider about the risk of C. diff infection. They may recommend taking probiotics to prevent C. diff.

Diarrhea can cause dehydration, so it’s important to drink lots of fluids if you develop diarrhea while taking Zyvox. You should also contact your healthcare provider if diarrhea continues past a couple of days or if it’s watery. They’ll likely recommend stopping Zyvox if they think you have a C. diff infection. You may need to take different antibiotics to treat C. diff and your original infection.

2. Headache

Headaches are a common side effect of many medications, including Zyvox. In studies, headaches occurred in up to 9% of adults taking Zyvox. 

If you experience headaches from Zyvox, you may find relief from over-the-counter (OTC) pain relievers such as ibuprofen (Advil, Motrin) or acetaminophen (Tylenol). But talk to your healthcare provider before taking these medications, to make sure they’re safe for you.

If your headache is severe or doesn’t respond to OTC pain relievers, talk to your healthcare provider. They can help determine whether Zyvox is causing the headaches or if there is another cause. 

3. Nausea and vomiting

Nausea and vomiting are also common Zyvox side effects. In clinical trials, up to 7% of adults had nausea and up to 9% reported vomiting. 

If you’re experiencing nausea or vomiting with Zyvox, try taking it with food. Eating smaller, more frequent meals throughout the day and staying hydrated can also help.

If you are vomiting many times a day or have nausea and vomiting that last multiple days, talk to your healthcare provider. These could be signs of more serious side effects of Zyvox. 

4. Blood cell problems

One rare side effect of Zyvox is a change in blood cell levels caused by abnormalities in bone marrow activity (myelosuppression). This happens when your bone marrow doesn’t make enough blood cells for your body to stay healthy. Your healthcare provider may do blood tests to determine if you’re experiencing any blood cell abnormalities. Stopping Zyvox can often reverse these problems, but you shouldn’t do so without talking to your provider first. 

If you’re experiencing blood cell problems, your blood tests may show:

• Anemia (low red blood cells)

• Leukopenia (low leukocytes, a type of white blood cell)

• Thrombocytopenia (low platelets)

• Pancytopenia (low white and red blood cells)

If you have existing bone marrow problems, a chronic infection, or you take other antibiotics, let your healthcare provider know. Abnormal blood cell levels are more likely in these situations. Blood cell problems are also more likely if you take Zyvox for more than 2 weeks. If you experience fever, sore throat, or fatigue while taking Zyvox, let your healthcare provider know. These may be signs of blood or bone marrow problems.

5. Nerve damage, especially in the eyes

Damage to the major nerve in the eye (optic neuropathy) is another rare side effect of Zyvox. Peripheral neuropathy (damage to nerves throughout the body) can also occur. It is most likely to happen if you take Zyvox for more than 28 days. 

Signs of optic neuropathy may include blurry vision or vision loss. You may also notice a change in how you see colors. If you notice any of these changes, contact your healthcare provider right away. They’ll likely refer you to an eye specialist to have your eyes checked.

Symptoms of peripheral neuropathy might include tingling or numbness in your hands or feet. If you have these symptoms, let your provider know. 

6. Serotonin syndrome

Zyvox can increase serotonin levels. Serotonin is a chemical that regulates several body functions, including your mood and sleep. But too much serotonin can lead to a potentially serious condition called serotonin syndrome.

Serotonin syndrome is rare, but it’s more likely to happen if you take multiple medications that raise serotonin levels. It’s also more likely with high medication doses. Medications that increase serotonin include antidepressants like selective serotonin reuptake inhibitors (SSRIs), tricyclic antidepressants (TCAs), and monoamine oxidase inhibitors (MAOIs). MAOIs and Zyvox shouldn’t be taken within two weeks of each other.

Serotonin syndrome is usually mild and can cause symptoms like sweating, tremors, and a fast heartbeat. In severe cases, however, it can cause confusion, high fever, and agitation. If you have mild symptoms of serotonin syndrome, contact your provider. And if your symptoms are severe, seek emergency care.

Before starting Zyvox, give your healthcare provider and pharmacist an up-to-date medication list. This will help them check whether you’re taking other medications that can increase serotonin. The list should include all prescription and OTC medications you take.

If you’re taking other medications that increase serotonin, your provider will likely recommend avoiding Zyvox. But if Zyvox is the only option, they may stop some of your other medications temporarily. Don’t make any changes to your medications without talking to your provider first.

7. Buildup of lactic acid

Lactic acidosis is a buildup of lactic acid in the blood. Lactic acid is a substance that’s made throughout the body. Usually, the liver and kidneys break it down to be used for energy. But if too much of it builds up, your blood becomes too acidic. This can be life-threatening.

Zyvox may cause lactic acidosis by causing the body to create too much lactic acid. This has to do with the way Zyvox prevents bacteria from growing. Signs of lactic acidosis may include repeated episodes of nausea or vomiting, confusion, tiredness, or fast breathing. If you experience any signs of lactic acidosis, seek medical help immediately. 

8. Seizures

Seizures are another rare side effect of Zyvox. This side effect is more likely if you already have a history of seizures or if you take other medications that increase seizure risk (also called lowering the seizure threshold). 

If you’re prescribed Zyvox, talk to your healthcare provider about your individual risk for seizures. They may recommend a different antibiotic if you're at high risk.

9. Low blood sugar

Zyvox may cause low blood sugar (hypoglycemia). It’s rare, but it’s more common in people with diabetes who use insulin or take other diabetes medications. Symptoms of hypoglycemia include shaking, sweating, and a fast heartbeat. 

If you experience hypoglycemia while taking Zyvox, you should treat it quickly. Typically, a blood sugar level below 70 mg/dL is considered too low. It’s a good idea to carry sugar tablets with you if you’re taking Zyvox, especially if you take diabetes medications. Four sugar tablets contain the recommended 15 grams of fast-acting sugar to treat hypoglycemia. Other good options include drinking half a cup of fruit juice or soda or eating a tablespoon of sugar or honey.

If you experience hypoglycemia, make sure to let your healthcare provider know. They may adjust the dose of your diabetes medication, or they may recommend stopping Zyvox. 

When should I contact my healthcare provider about side effects from Zyvox?

If you experience any severe Zyvox side effects, such as watery diarrhea, tiredness, or blurry vision, contact your healthcare provider immediately. Other symptoms — like extreme confusion, fever, or vomiting — may also need immediate medical treatment.

You should also contact your provider if you have mild Zyvox side effects that don’t improve over time. This includes headache and nausea. Even though these side effects can often be managed at home, you may need further evaluation if they last longer than a few days.

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Written by:

Austin Ulrich, PharmD, BCACP

Austin Ulrich, PharmD, BCACP, is a board-certified ambulatory care clinical pharmacist. In his early career, he provided direct patient care in a variety of settings, including hospital and community pharmacies, and in a primary care clinic as a clinical pharmacist.

Edited by:

Amy B. Gragnolati, PharmD, BCPS

Amy Gragnolati, PharmD, BCPS, is a pharmacy editor for GoodRx. Amy currently holds her pharmacist license in Georgia and California.

Reviewed by:

Tegan Smedley, PharmD, APh

Tegan Smedley, PharmD, APh, has 10 years of experience as a pharmacist. She has worked in a variety of settings, including retail, hospital, and ambulatory care.

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