Linzolid400 mg

Linzolid is an oxazolidinone antibiotic reserved for the treatment of serious infections caused by susceptible gram-positive bacteria, including resistant organisms such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VRE). Linzolid is not indicated for gram-negative infections.

FDA-approved / Established indications

• Nosocomial (hospital-acquired) pneumonia caused by Staphylococcus aureus (methicillin-susceptible and resistant strains) or Streptococcus pneumoniae
• Community-acquired pneumonia caused by susceptible strains of Streptococcus pneumoniae or Staphylococcus aureus
• Complicated skin and skin structure infections
• Uncomplicated skin and skin structure infections
• Vancomycin-resistant Enterococcus faecium (VRE) infections, including cases with concurrent bacteraemia

Off-label / reserve use

Linzolid is also used off-label, generally as part of combination regimens under specialist supervision, for multidrug-resistant tuberculosis and certain difficult-to-treat bone/joint or central nervous system gram-positive infections. Because of the risk of resistance development and serious toxicity, Linzolid should be reserved for infections proven or strongly suspected to be caused by susceptible gram-positive organisms, ideally guided by culture and sensitivity results.

Each tablet/capsule or vial of injectable/oral suspension contains Linezolid as the active ingredient, available in strengths and formulations such as 200 mg, 400 mg, and 600 mg tablets, 600 mg/300 mL intravenous infusion, and 100 mg/5 mL oral suspension, along with pharmaceutically approved inactive excipients.

Linzolid is a synthetic antibacterial agent belonging to the oxazolidinone class. It was one of the first antibiotics developed specifically to target multidrug-resistant gram-positive bacteria, including MRSA and VRE, for which few oral treatment options previously existed. Linzolid is available as oral tablets, an oral suspension, and an intravenous infusion, offering equivalent bioavailability between the oral and IV routes, which allows for convenient switching from IV to oral therapy.

Because Linzolid carries important safety considerations — including bone marrow suppression, nerve toxicity with prolonged use, and interactions with serotonergic and adrenergic drugs — it is typically used as a reserve agent under close medical supervision rather than as first-line therapy.

Linzolid belongs to the oxazolidinone class of synthetic antibacterial agents, a distinct antibiotic class active against gram-positive bacteria, including strains resistant to other antibiotic classes.

Linezolid exerts its antibacterial effect by binding to the bacterial 23S ribosomal RNA of the 50S ribosomal subunit, thereby preventing formation of the functional 70S initiation complex that is essential for bacterial protein synthesis. This mechanism is unique among protein synthesis inhibitors and results in a low potential for cross-resistance with other antibiotic classes (such as macrolides, aminoglycosides, and chloramphenicol).

Linezolid is bacteriostatic against enterococci and staphylococci, and bactericidal against most streptococcal strains.

Pharmacokinetics

• Absorption: Rapidly and almost completely absorbed after oral administration, with bioavailability of approximately 100%, allowing direct IV-to-oral dose equivalence
• Distribution: Widely distributed to well-perfused tissues; moderate protein binding (~31%)
• Metabolism: Metabolized primarily via non-enzymatic oxidation (not significantly via the cytochrome P450 system), reducing the potential for many CYP-mediated drug interactions
• Elimination: Eliminated mainly via non-renal clearance with a plasma half-life of approximately 5-7 hours in adults

Linzolid tablets can be taken with or without food. The oral suspension should be mixed gently before each dose. The intravenous formulation is given as an infusion over 30 to 120 minutes and should not be mixed with other drugs in the same line unless compatibility has been confirmed. Complete the full prescribed course of Linzolid as directed by the physician.

Linzolid is a reversible, non-selective inhibitor of monoamine oxidase (MAO), which is responsible for its most clinically significant drug interactions.

Serotonin syndrome risk

Concurrent use of Linzolid with serotonergic drugs — including SSRIs, SNRIs, tricyclic antidepressants, MAO inhibitors, triptans, tramadol, meperidine (pethidine), buspirone, and certain opioids — can cause serotonin syndrome, a potentially life-threatening condition. If such combination cannot be avoided, close monitoring for symptoms such as agitation, tremor, hyperreflexia, fever, and autonomic instability is required.

Hypertensive crisis risk

Because of its MAO-inhibiting activity, Linzolid can interact with adrenergic and sympathomimetic agents (e.g., pseudoephedrine, phenylephrine, dopamine, epinephrine) and with tyramine-rich foods, raising the risk of a sudden, severe rise in blood pressure (hypertensive crisis). Blood pressure should be monitored closely if such agents cannot be avoided, and tyramine-rich foods (aged cheeses, cured/fermented meats, tap beers, soy sauce, and similar products) should be limited during treatment.

Other interactions

• Concurrent or recent (within 2 weeks) use of monoamine oxidase inhibitors is contraindicated (see Contraindications).
• Linzolid does not significantly interact with the cytochrome P450 enzyme system, so interactions through that pathway are uncommon.

Common side effects

• Diarrhoea
• Headache
• Nausea and vomiting
• Oral or vaginal candidiasis (thrush)
• Taste alteration / tongue discolouration
• Insomnia

Serious side effects (seek prompt medical attention)

• Myelosuppression: unusual bleeding/bruising, pale skin, fatigue, or signs of infection (see Precautions and Warnings)
• Peripheral or optic neuropathy: numbness/tingling in the hands or feet, blurred vision, or changes in colour vision, particularly with treatment beyond 28 days
• Lactic acidosis: recurrent nausea, vomiting, unexplained rapid breathing, or low bicarbonate levels
• Serotonin syndrome (with interacting drugs): agitation, tremor, sweating, fast heart rate, high fever
• Severe diarrhoea associated with Clostridioides difficile infection
• Signs of a severe allergic reaction: rash, swelling of the face/throat, difficulty breathing

Pregnancy: There is no formal FDA pregnancy category assigned under the current labeling system. Available human data have not identified a clear drug-associated risk of major birth defects, but animal studies at high exposures have shown adverse effects on the developing foetus. Linzolid should be used during pregnancy only if clearly needed and the potential benefit justifies the potential risk to the foetus; use only under direct physician supervision.

Lactation: Linzolid passes into breast milk. Because of the potential for adverse effects (such as diarrhoea or vomiting) in a breastfed infant, a decision should be made, in consultation with a physician, whether to continue breastfeeding or continue Linzolid therapy, weighing the importance of treatment to the mother against the possible risk to the infant, with monitoring of the infant if breastfeeding continues.

Myelosuppression

Linzolid has been associated with myelosuppression (including anaemia, leukopenia, pancytopenia, and thrombocytopenia), particularly with courses longer than 14 days. Complete blood counts should be monitored weekly, especially in patients receiving prolonged therapy, those with pre-existing bone marrow suppression, patients on other myelosuppressive drugs, or those with chronic infection who have received prior antibiotic therapy.

Peripheral and optic neuropathy

Peripheral and optic neuropathy, sometimes irreversible, has been reported, primarily in patients treated with Linzolid for longer than the recommended maximum duration of 28 days. Patients should promptly report any visual changes, and ophthalmologic evaluation is recommended if symptoms occur; treatment beyond 28 days should only continue with close specialist monitoring.

Lactic acidosis

Lactic acidosis has been reported rarely with Linzolid use. Patients who develop recurrent nausea or vomiting, unexplained acidosis, or a low bicarbonate level while on Linzolid should seek prompt medical evaluation.

Serotonin syndrome and hypertensive crisis

See Drug Interactions for detailed guidance on serotonergic and sympathomimetic drug interactions and dietary tyramine precautions related to Linzolid's monoamine oxidase-inhibiting activity.

Other precautions

• Clostridioides difficile-associated diarrhoea has been reported with almost all antibacterial agents, including Linzolid, and may range from mild diarrhoea to fatal colitis.
• Hypoglycaemia has been reported in diabetic patients receiving insulin or oral hypoglycaemic agents together with Linzolid; blood glucose should be monitored.
• Development of drug-resistant bacteria: use Linzolid only for infections proven or strongly suspected to be caused by susceptible gram-positive bacteria.

Antibiotic stewardship: Take Linzolid exactly as prescribed by your physician; do not stop, extend, skip doses, or share this medicine with others without medical advice.

There is limited clinical experience with Linzolid overdose. Supportive care is recommended, along with maintenance of glomerular filtration. Haemodialysis may modestly remove Linzolid from circulation but is not expected to provide significant clinical benefit. If an overdose of Linzolid is suspected, seek immediate medical attention or contact a poison control centre/emergency services; do not attempt home treatment.

Store at room temperature (below 30°C), away from light and moisture. Protect the oral suspension and injection from freezing. Keep out of reach of children.

Renal impairment

No dose adjustment of Linzolid is generally required in renal impairment; however, the two primary metabolites may accumulate in patients with severe renal impairment (including those on dialysis), and the clinical significance of this is not fully established. Linzolid should be given after haemodialysis sessions since dialysis removes a portion of the drug.

Hepatic impairment

No dose adjustment is required for mild to moderate hepatic impairment. Linzolid has not been studied in severe hepatic impairment; use with caution and only if the expected benefit outweighs the theoretical risk.

Elderly patients

No dose adjustment is required based on age alone; however, elderly patients may be at greater risk of myelosuppression and should have blood counts monitored, particularly with prolonged therapy.

Pediatric patients

See Pediatric Uses for age- and weight-based dosing information.

Treatment duration with Linzolid depends on the indication and clinical response, typically ranging from 10-14 days for pneumonia and skin/skin structure infections, up to 14-28 days for vancomycin-resistant Enterococcus faecium infections. Treatment beyond 28 days is generally not recommended due to increased risk of peripheral/optic neuropathy and myelosuppression, and should only continue under close specialist supervision when necessary. Always complete the course exactly as directed by the physician.

Oxazolidinone antibiotic (synthetic antibacterial)

Linezolid binds to the 23S ribosomal RNA of the bacterial 50S ribosomal subunit, blocking formation of the 70S initiation complex required for bacterial protein synthesis. This unique binding site means Linezolid generally does not share cross-resistance with other classes of protein synthesis inhibitors. It is bacteriostatic against staphylococci and enterococci, and bactericidal against most streptococci.

Linzolid is approved for use in pediatric patients from birth through 17 years of age for the same indications as adults (susceptible pneumonia, complicated/uncomplicated skin and skin structure infections, and vancomycin-resistant Enterococcus faecium infections), using weight-based dosing.

• Full-term neonates and children (birth to 11 years): 10 mg/kg every 8 hours
• Preterm neonates (<7 days): 10 mg/kg every 12 hours, increasing to every 8 hours as the child reaches 7 days of age, based on clinical response
• Adolescents (≥12 years): Adult dosing (600 mg every 12 hours) applies

Linzolid has variable and unpredictable penetration into cerebrospinal fluid and is not recommended for the empiric treatment of central nervous system infections in children. Monitor pediatric patients for the same safety concerns as adults, including blood counts with prolonged therapy.