Zyvoxid (Linezolid): Uses, Dosage & Side Effects
An oxazolidinone antibiotic reserved for serious Gram-positive infections including MRSA and VRE
Zyvoxid (linezolid) is a synthetic oxazolidinone antibiotic used to treat serious infections caused by Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). It is indicated for hospital-acquired and community-acquired pneumonia, as well as complicated skin and soft tissue infections. Linezolid has a unique mechanism of action with no cross-resistance to other antibiotic classes, making it a valuable reserve antibiotic. It requires a prescription, and treatment should be initiated only by physicians experienced in the management of serious infections.
Quick Facts: Zyvoxid (Linezolid)
Key Takeaways
- Linezolid is a reserve antibiotic effective against multi-drug resistant Gram-positive bacteria including MRSA and VRE, and should only be used when first-line antibiotics are unsuitable.
- The standard dose is 600 mg twice daily (every 12 hours) for 10-14 days, with a maximum treatment duration of 28 days due to risk of serious adverse effects.
- Regular blood count monitoring is mandatory during treatment because linezolid can suppress bone marrow function, particularly affecting platelet production.
- Linezolid must not be combined with MAO inhibitors or serotonergic drugs (SSRIs, opioids, triptans) due to the risk of potentially life-threatening serotonin syndrome.
- Patients should avoid tyramine-rich foods (aged cheese, yeast extract, soy sauce, draft beer, red wine) to prevent dangerous blood pressure elevations.
What Is Zyvoxid and What Is It Used For?
Zyvoxid contains the active substance linezolid, which belongs to a class of antibiotics called oxazolidinones. Unlike most other antibiotics, linezolid works by binding to the bacterial ribosome at a unique site on the 23S ribosomal RNA of the 50S subunit, preventing the formation of the 70S initiation complex that is essential for bacterial protein synthesis. This distinctive mechanism of action means that there is virtually no cross-resistance with other classes of antibiotics, making linezolid particularly valuable against multi-drug resistant organisms.
Linezolid demonstrates excellent activity against a wide range of Gram-positive pathogens, including Staphylococcus aureus (both methicillin-susceptible and methicillin-resistant strains), Streptococcus pneumoniae (including penicillin-resistant strains), Streptococcus pyogenes, Enterococcus faecium (including vancomycin-resistant strains), and Enterococcus faecalis. It is bacteriostatic against most susceptible organisms but exhibits bactericidal activity against certain streptococcal species.
The primary clinical indications for linezolid include hospital-acquired pneumonia (nosocomial pneumonia), community-acquired pneumonia, and complicated skin and soft tissue infections. It is particularly important in the treatment of infections caused by MRSA and VRE, where treatment options are limited. The World Health Organization (WHO) classifies linezolid in the Reserve group of its AWaRe (Access, Watch, Reserve) classification, meaning it should be reserved for use when other antibiotics have failed or are not suitable.
Linezolid has nearly 100% oral bioavailability, meaning that the oral tablet formulation achieves blood levels equivalent to intravenous administration. This allows patients to be switched from intravenous to oral therapy without dose adjustment, facilitating earlier hospital discharge and outpatient treatment of serious infections. Peak plasma concentrations are reached within 1 to 2 hours after oral administration, and the elimination half-life is approximately 5 to 7 hours.
What Should You Know Before Taking Zyvoxid?
Contraindications
Zyvoxid must not be used in the following situations:
- Allergy to linezolid or any of the excipients in the formulation (maize starch, microcrystalline cellulose, hydroxypropylcellulose, sodium starch glycolate, magnesium stearate, hypromellose, titanium dioxide, macrogol 400, carnauba wax).
- Concurrent use of MAO inhibitors: You must not take linezolid if you are currently taking or have taken any monoamine oxidase inhibitor (MAOI) within the past 14 days. MAOIs include phenelzine, isocarboxazid, selegiline, and moclobemide, which may be used to treat depression or Parkinson's disease.
- Breastfeeding: Linezolid passes into breast milk and may affect the nursing infant. Women should not breastfeed during treatment with linezolid.
Warnings and Precautions
Before starting treatment with linezolid, inform your doctor if any of the following apply to you. Your doctor may need to monitor your health more closely or consider an alternative treatment:
- High blood pressure (hypertension), whether treated or untreated, as linezolid has mild MAO inhibitory properties that can affect blood pressure regulation.
- Overactive thyroid gland (hyperthyroidism), as the combination with linezolid's MAO inhibitory activity may precipitate hypertensive crises.
- Phaeochromocytoma (a tumour of the adrenal gland) or carcinoid syndrome, conditions that involve excessive catecholamine or serotonin production.
- Psychiatric conditions such as bipolar disorder, schizoaffective disorder, or confusional states, as linezolid may exacerbate these conditions.
- History of seizures, as convulsions have been reported in patients treated with linezolid.
- Liver or kidney problems, particularly if you are on dialysis. Linezolid should be taken after dialysis sessions.
- Anaemia (low red blood cell count) or tendency to bruise or bleed easily, as linezolid can suppress blood cell production.
- Low sodium levels (hyponatraemia) or use of diuretics such as hydrochlorothiazide that lower sodium levels.
Pregnancy and Breastfeeding
The effects of linezolid during pregnancy have not been adequately studied in humans. Animal studies have shown some evidence of reproductive toxicity, but the relevance to human pregnancy is uncertain. Linezolid should not be used during pregnancy unless the potential benefit justifies the potential risk to the foetus. Your doctor will carefully weigh the risks and benefits before prescribing this medication to a pregnant woman.
Linezolid and its metabolites are excreted in breast milk. Because of the potential for serious adverse reactions in nursing infants, breastfeeding is contraindicated during treatment with linezolid. Women who need to take linezolid should discuss alternative feeding options with their healthcare provider.
If you are pregnant, think you may be pregnant, or are planning to have a baby, seek advice from your doctor before taking this medicine.
Driving and Operating Machinery
Linezolid may cause dizziness or visual disturbances. If you experience these effects, you should not drive or operate machinery. Your ability to perform these activities may be impaired even if you do not feel dizzy, so exercise caution until you know how linezolid affects you.
How Does Zyvoxid Interact with Other Drugs?
Linezolid is a reversible, non-selective inhibitor of monoamine oxidase (MAO), although this activity is relatively weak compared to dedicated MAO inhibitor drugs. This pharmacological property is responsible for the majority of its clinically significant drug interactions. Because MAO enzymes are involved in the breakdown of neurotransmitters such as serotonin, noradrenaline, and dopamine, linezolid can potentiate the effects of drugs that increase the levels of these neurotransmitters.
Major Interactions (Contraindicated or Avoid)
| Drug / Drug Class | Risk | Recommendation |
|---|---|---|
| MAO inhibitors (phenelzine, isocarboxazid, selegiline, moclobemide) | Hypertensive crisis, serotonin syndrome | Contraindicated. Do not use within 14 days of each other. |
| SSRIs (fluoxetine, sertraline, paroxetine, citalopram, fluvoxamine) | Serotonin syndrome | Avoid combination. If essential, monitor closely for signs of serotonin syndrome. |
| SNRIs (venlafaxine, duloxetine) | Serotonin syndrome | Avoid combination. Consider alternative antibiotic or antidepressant. |
| Tricyclic antidepressants (amitriptyline, clomipramine, imipramine, doxepin) | Serotonin syndrome, blood pressure changes | Avoid combination. Monitor blood pressure and serotonin symptoms if unavoidable. |
| Opioids (pethidine, tramadol, fentanyl) | Serotonin syndrome | Avoid serotonergic opioids. Use non-serotonergic alternatives (e.g. morphine, oxycodone) if needed. |
| Triptans (sumatriptan, zolmitriptan) | Serotonin syndrome | Avoid combination during linezolid treatment. |
Moderate Interactions (Use with Caution)
| Drug / Drug Class | Risk | Recommendation |
|---|---|---|
| Pseudoephedrine, phenylpropanolamine (decongestants) | Elevated blood pressure | Monitor blood pressure. Avoid if possible. |
| Sympathomimetic bronchodilators (salbutamol, terbutaline, fenoterol) | Elevated blood pressure, increased heart rate | Use with caution. Monitor cardiovascular parameters. |
| Adrenaline (epinephrine), noradrenaline, dopamine, dobutamine | Hypertensive response | Use reduced doses if clinically necessary. Monitor blood pressure closely. |
| Buspirone (anxiolytic) | Serotonin syndrome | Use with caution and monitor for serotonergic symptoms. |
| Warfarin (anticoagulant) | Altered INR values | Monitor INR more frequently during concurrent use. |
| Rifampicin (antibiotic) | Reduced linezolid plasma levels | Clinical significance uncertain. Monitor therapeutic response. |
Food and Alcohol Interactions
Because linezolid has MAO inhibitory properties, patients should avoid consuming large quantities of tyramine-rich foods during treatment. Tyramine is a naturally occurring amine found in certain foods that is normally broken down by MAO enzymes in the gut. When MAO is inhibited by linezolid, tyramine can accumulate and cause a sudden, potentially dangerous increase in blood pressure (hypertensive crisis).
Foods and beverages to avoid or limit include:
- Aged cheeses such as cheddar, blue cheese, Stilton, Camembert, Brie, and parmesan
- Yeast extracts such as Marmite, Vegemite, and brewer's yeast supplements
- Fermented soy products such as soy sauce, miso, tempeh, and tofu
- Fermented or cured meats such as salami, pepperoni, chorizo, and dry-cured sausages
- Draft (unpasteurised) beer and red wine
- Sauerkraut and other fermented vegetables
What Is the Correct Dosage of Zyvoxid?
Adults
Standard Adult Dosage
The recommended dose is 600 mg (one film-coated tablet) twice daily, taken approximately every 12 hours. Swallow the tablet whole with water. Linezolid can be taken with or without food.
| Indication | Dose | Duration |
|---|---|---|
| Hospital-acquired pneumonia | 600 mg twice daily | 10-14 days |
| Community-acquired pneumonia | 600 mg twice daily | 10-14 days |
| Complicated skin and soft tissue infections | 600 mg twice daily | 10-14 days (up to 28 days) |
If you are undergoing kidney dialysis, linezolid should be taken after the dialysis session. No dose adjustment is required for patients with renal or hepatic impairment, but close monitoring is recommended.
During treatment, your doctor will order regular blood tests (typically weekly) to monitor your complete blood count, as linezolid can suppress blood cell production. If treatment extends beyond 28 days, your doctor should also arrange for regular eye examinations to check for optic neuropathy.
Children and Adolescents
Paediatric Use
Linezolid is not routinely recommended for use in children and adolescents under 18 years of age. The safety and efficacy in this population have not been sufficiently established. In exceptional circumstances, paediatric use may be considered by a specialist, typically using weight-based dosing with an oral suspension formulation.
Elderly Patients
No dose adjustment is required for elderly patients based on age alone. However, elderly patients may be more susceptible to adverse effects, particularly myelosuppression and neuropathy. Closer monitoring of blood counts and neurological function is advisable in this population.
Missed Dose
If you forget to take a dose of linezolid, take it as soon as you remember. Then take the next dose 12 hours later and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. Maintaining consistent 12-hour intervals between doses is important for maintaining effective drug levels in your blood.
Overdose
If you take more linezolid than prescribed, or if a child accidentally ingests the medication, contact your local emergency services or a poison control centre immediately. Symptoms of overdose may be an exaggeration of the known side effects. There is no specific antidote for linezolid overdose, and treatment is supportive. Linezolid is partially removed by haemodialysis.
What Are the Side Effects of Zyvoxid?
Like all medicines, linezolid can cause side effects, although not everyone gets them. Some side effects can be serious and require immediate medical attention. The following section lists side effects by how frequently they occur, based on clinical trial data and post-marketing surveillance reports.
Common
May affect up to 1 in 10 people
- Headache
- Diarrhoea, nausea, or vomiting
- Metallic taste in the mouth (dysgeusia)
- Fungal infections (oral or vaginal thrush)
- Anaemia (low red blood cell count)
- Decreased platelet count (thrombocytopenia)
- Insomnia (difficulty sleeping)
- Increased blood pressure
- Dizziness
- Abdominal pain (localised or generalised)
- Constipation or dyspepsia (indigestion)
- Localised pain
- Fever
- Skin rash or itching (pruritus)
- Changes in blood test results (liver enzymes, kidney function, blood glucose, protein levels)
Uncommon
May affect up to 1 in 100 people
- Severe skin reactions or swelling of the face and throat (angioedema)
- Vision problems including blurred vision
- Seizures (convulsions)
- Inflammation of the pancreas (pancreatitis)
- Antibiotic-associated colitis (including pseudomembranous colitis with bloody diarrhoea)
- Transient ischaemic attacks (TIA)
- Tinnitus (ringing in the ears)
- Sore throat, mouth ulcers
- Numbness or tingling (paraesthesia)
- Decreased white blood cell count (leucopenia)
- Swollen, sore, or discoloured tongue
- Dry mouth, increased thirst
- Increased sweating, chills
- Increased urination frequency
- Low sodium levels (hyponatraemia)
- Kidney failure
- Flatulence, stomach pain
- Heart rhythm changes (e.g. tachycardia)
- Fatigue, weakness
- Dermatitis (tender, red, flaking skin)
Rare
May affect up to 1 in 1,000 people
- Wheezing or difficulty breathing (bronchospasm)
- Vasculitis (raised, purplish rash from blood vessel inflammation)
- Lactic acidosis (recurrent nausea, vomiting, abdominal pain, rapid breathing)
- Rhabdomyolysis (unexplained muscle pain, tenderness, weakness with dark urine)
- Superficial tooth discolouration (removable by professional dental cleaning)
- Visual field defects
Frequency Not Known
Cannot be estimated from available data
- Serotonin syndrome (agitation, confusion, tremor, muscle rigidity, rapid heart rate, fever, diarrhoea) - particularly with concurrent serotonergic drugs
- Colour vision changes (colour blindness)
- Difficulty seeing fine detail (reduced visual acuity)
- Hair loss (alopecia)
- Peripheral neuropathy (numbness, tingling in extremities) - typically with treatment exceeding 28 days
- Optic neuropathy - typically with treatment exceeding 28 days
Contact your doctor or seek emergency care immediately if you experience: difficulty breathing or wheezing; swelling of the face, lips, tongue, or throat; severe skin reactions; sudden vision changes; bloody or watery diarrhoea; unexplained muscle pain with dark urine; signs of serotonin syndrome (confusion, agitation, tremor, rapid heartbeat, fever); or symptoms of lactic acidosis (persistent nausea, vomiting, abdominal pain, rapid breathing).
Long-term use considerations: Patients treated with linezolid for more than 28 days have an increased risk of developing peripheral neuropathy (numbness, tingling, or pain in the hands and feet) and optic neuropathy (visual disturbances including blurred vision and colour vision changes). These neurological effects may be irreversible in some cases. If you are prescribed linezolid for an extended course, your doctor should arrange regular neurological assessments and ophthalmological examinations.
Linezolid-induced myelosuppression, particularly thrombocytopenia, is dose- and duration-dependent. It is more likely to occur in patients with pre-existing bone marrow suppression, those receiving concurrent myelosuppressive drugs, and those treated for longer than 14 days. Weekly monitoring of the complete blood count is essential throughout treatment.
How Should You Store Zyvoxid?
Keep Zyvoxid tablets out of the sight and reach of children. This medicine does not require any special storage conditions and should be stored at normal room temperature. Do not use Zyvoxid after the expiry date stated on the carton or blister packaging after "EXP". The expiry date refers to the last day of that month.
Do not dispose of medicines via wastewater or household waste. Ask your pharmacist how to dispose of medicines you no longer use. These measures help to protect the environment. If you notice any deterioration in the appearance of the tablets (discolouration, crumbling, unusual odour), do not take them and consult your pharmacist.
What Does Zyvoxid Contain?
The active substance is linezolid. Each film-coated tablet contains 600 mg of linezolid.
The other ingredients (excipients) are:
- Tablet core: Maize starch, microcrystalline cellulose (E460), hydroxypropylcellulose (E463), sodium starch glycolate type A, magnesium stearate (E572)
- Film coating: Hypromellose (E464), titanium dioxide (E171), macrogol 400, carnauba wax (E903)
Appearance: Zyvoxid 600 mg tablets are white, oval, film-coated tablets engraved with "ZYV" on one side and "600" on the other side.
Packaging: Zyvoxid is available in blister packs of 10, 20, 30, 50, 60, or 100 tablets, and in HDPE bottles with polypropylene screw caps containing 10, 14, 20, 24, 30, 50, 60, or 100 tablets. Not all pack sizes may be marketed in your country.
Frequently Asked Questions About Zyvoxid
Zyvoxid (linezolid) is an oxazolidinone antibiotic used to treat serious infections caused by Gram-positive bacteria. Its main indications include hospital-acquired pneumonia (nosocomial pneumonia), community-acquired pneumonia, and complicated skin and soft tissue infections. It is particularly valuable for treating infections caused by multi-drug resistant organisms such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). Linezolid is classified as a reserve antibiotic by the WHO and should only be used when first-line treatments are ineffective or unsuitable.
Linezolid is classified in the WHO Reserve group because it has a unique mechanism of action effective against multi-drug resistant bacteria. To prevent the emergence of linezolid-resistant organisms and preserve its clinical utility, it is reserved for serious infections that do not respond to first-line antibiotics. Resistance to linezolid remains rare but has been reported, particularly in healthcare settings with high linezolid usage. Appropriate antimicrobial stewardship is essential to maintain the effectiveness of this important antibiotic.
The most clinically significant side effects of linezolid include myelosuppression (suppression of bone marrow function), particularly thrombocytopenia (low platelet count) and anaemia, which require weekly blood count monitoring. With prolonged use beyond 28 days, there is a risk of peripheral neuropathy (numbness or tingling in the extremities) and optic neuropathy (vision changes), which may be irreversible. Serotonin syndrome can occur when linezolid is combined with serotonergic medications. Lactic acidosis and rhabdomyolysis are rare but serious complications. Report any visual changes, unusual bleeding or bruising, unexplained muscle pain, or neurological symptoms to your doctor immediately.
Linezolid has weak monoamine oxidase (MAO) inhibitory activity, which makes it potentially dangerous to combine with serotonergic medications. It is contraindicated with MAO inhibitors and should generally be avoided with SSRIs, SNRIs, tricyclic antidepressants, triptans, and serotonergic opioids (pethidine, tramadol). The combination can cause serotonin syndrome, a potentially life-threatening condition characterised by agitation, confusion, tremor, rapid heart rate, high blood pressure, fever, and diarrhoea. If you are taking any antidepressant, inform your doctor before starting linezolid so that an alternative antibiotic or temporary discontinuation of the antidepressant can be considered.
Yes. Because linezolid has mild MAO inhibitory activity, patients should avoid large amounts of tyramine-rich foods during treatment. These include aged cheeses (cheddar, blue cheese, parmesan), yeast extracts (Marmite, Vegemite), fermented soy products (soy sauce, miso, tempeh), fermented or cured meats (salami, pepperoni), draft beer, red wine, and sauerkraut. Consuming large amounts of tyramine while taking linezolid can cause a dangerous rise in blood pressure. If you develop a severe, throbbing headache after eating or drinking, seek immediate medical attention as this may indicate a hypertensive reaction.
The standard treatment course for linezolid is 10 to 14 days, though it may be extended up to 28 days depending on the type and severity of infection. The safety and efficacy of linezolid treatment beyond 28 days have not been established in clinical trials. Prolonged use significantly increases the risk of myelosuppression (bone marrow suppression), peripheral neuropathy, and optic neuropathy. If your doctor prescribes linezolid for longer than 28 days, you will need regular blood tests and eye examinations. Never extend or shorten your treatment course without consulting your doctor.
References
- World Health Organization (WHO). Model List of Essential Medicines - 23rd List. WHO, 2023. Available at: who.int/publications
- European Medicines Agency (EMA). Zyvoxid - Summary of Product Characteristics. EMA, 2024. Available at: ema.europa.eu
- U.S. Food and Drug Administration (FDA). Zyvox (Linezolid) - Prescribing Information. FDA, 2023. Available at: accessdata.fda.gov
- British National Formulary (BNF). Linezolid Monograph. NICE, 2024. Available at: bnf.nice.org.uk
- Liu C, Bayer A, Cosgrove SE, et al. Clinical Practice Guidelines by the IDSA for the Treatment of Methicillin-Resistant Staphylococcus aureus Infections in Adults and Children. Clinical Infectious Diseases. 2011;52(3):e18-e55. doi:10.1093/cid/ciq146
- Wunderink RG, Niederman MS, Kollef MH, et al. Linezolid in Methicillin-Resistant Staphylococcus aureus Nosocomial Pneumonia: A Randomized, Controlled Study. Clinical Infectious Diseases. 2012;54(5):621-629. doi:10.1093/cid/cir895
- World Health Organization (WHO). AWaRe Classification of Antibiotics for Evaluation and Monitoring of Use. WHO, 2023. Available at: who.int/publications
- Bressler AM, Zimmer SM, Gilmore JL, Somani J. Peripheral Neuropathy Associated with Prolonged Use of Linezolid. The Lancet Infectious Diseases. 2004;4(8):528-531. doi:10.1016/S1473-3099(04)01109-0
Editorial Team
This article was written and reviewed by the iMedic Medical Editorial Team, comprising licensed physicians specialising in clinical pharmacology, infectious disease medicine, and antimicrobial stewardship.
Evidence standard: This article is based on Level 1A evidence (systematic reviews and meta-analyses of randomised controlled trials) and adheres to international clinical guidelines from WHO, EMA, FDA, BNF, and IDSA. All medical claims are supported by peer-reviewed research and authoritative pharmaceutical references.
Conflict of interest: The iMedic editorial team has no financial relationships with pharmaceutical companies. This content is independently produced with no commercial funding or sponsorship.
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