Linezolid
linezolid tablets, injection, and oral suspension (Zyvox)
Indications
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Nosocomial pneumonia caused by S. aureus (MRSA/MSSA) or S. pneumoniae | Adults and pediatrics (birth and older) | Monotherapy (add Gram-negative cover if suspected) | FDA Approved |
| Community-acquired pneumonia caused by S. pneumoniae (including MDRSP) or S. aureus (MSSA only) | Adults and pediatrics (birth and older) | Monotherapy or combination | FDA Approved |
| Complicated skin & skin structure infections (cSSSI) including diabetic foot infections (without osteomyelitis), caused by MRSA, MSSA, S. pyogenes, or S. agalactiae | Adults and pediatrics (birth and older) | Monotherapy | FDA Approved |
| Uncomplicated skin & skin structure infections (uSSSI) caused by S. aureus (MSSA) or S. pyogenes | Adults and pediatrics (5 years and older) | Oral only | FDA Approved |
| Vancomycin-resistant Enterococcus faecium (VRE) infections including concurrent bacteremia | Adults and pediatrics (birth and older) | Monotherapy | FDA Approved |
Linezolid is the first oxazolidinone antibiotic, approved in 2000, and remains a critical agent for serious Gram-positive infections, particularly when vancomycin resistance or intolerance limits other options. Its complete oral bioavailability enables seamless IV-to-oral step-down, making it especially valuable for outpatient completion of courses that require parenteral initiation. Linezolid has no clinically meaningful activity against Gram-negative organisms, and concurrent Gram-negative coverage must be provided when mixed infections are suspected.
MRSA osteomyelitis / prosthetic joint infection: Used as oral step-down therapy or in combination regimens for bone and joint MRSA infections. Evidence quality: Moderate (IDSA MRSA guideline 2011; case series).
MRSA/VRE meningitis or CNS infections: Linezolid achieves variable CSF concentrations (reported ~70% of plasma in some adult studies); the FDA PI notes therapeutic levels were not consistently achieved in pediatric CSF. Used when vancomycin fails or is not tolerated. Evidence quality: Low (case reports; variable PK data).
Multidrug-resistant and extensively drug-resistant tuberculosis: Component of MDR-TB/XDR-TB regimens (WHO Group A agent); prolonged courses with close monitoring for neuropathy and myelosuppression. Evidence quality: High (Nix-TB trial; WHO 2022 guideline).
Nocardiosis: Used in combination regimens for disseminated or CNS nocardiosis. Evidence quality: Low (case series).
Dosing
Adult Dosing — By Clinical Scenario
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Nosocomial pneumonia (MRSA/MSSA/S. pneumoniae) | 600 mg IV or PO q12h | 600 mg q12h | 1,200 mg/day | Duration: 10–14 days; add Gram-negative cover if suspected IV-to-oral switch with no dose change (100% bioavailability) |
| Community-acquired pneumonia (CAP) | 600 mg IV or PO q12h | 600 mg q12h | 1,200 mg/day | Duration: 10–14 days For MSSA-caused CAP only (not MRSA CAP per FDA label) |
| Complicated SSTI (including MRSA) | 600 mg IV or PO q12h | 600 mg q12h | 1,200 mg/day | Duration: 10–14 days; not approved for SSTI with concurrent osteomyelitis Includes diabetic foot infections without bone involvement |
| Uncomplicated SSTI | 400 mg PO q12h | 400 mg PO q12h | 800 mg/day | Duration: 10–14 days; oral only Lower dose than complicated infections |
| VRE (E. faecium) infections including bacteremia | 600 mg IV or PO q12h | 600 mg q12h | 1,200 mg/day | Duration: 14–28 days Longer courses increase myelosuppression risk; monitor CBC weekly |
| MDR/XDR tuberculosis (off-label) | 600 mg PO daily | 600 mg daily (or 300 mg daily for toxicity reduction) | 600 mg/day | WHO Group A agent; used for ≥6 months in MDR-TB regimens High neuropathy and myelosuppression rates with prolonged use; dose reduction to 300 mg/day may mitigate |
Pediatric Dosing
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Preterm neonates <7 days (<34 wks GA) | 10 mg/kg IV/PO q12h | 10 mg/kg q8h (by day 7 of life) | Do not exceed adult dose | Lower clearance in preterm neonates; increase to q8h by day 7 or if sub-optimal response Per FDA PI |
| Full-term neonates and infants <12 years — all indications except uSSSI | 10 mg/kg IV/PO q8h | 10 mg/kg q8h | 600 mg per dose | Duration per indication (10–28 days) Use oral suspension for accurate weight-based dosing |
| Children 5–11 years — uSSSI | 10 mg/kg PO q12h | 10 mg/kg q12h | 600 mg per dose | Duration: 10–14 days; oral only |
| Children <5 years — uSSSI | 10 mg/kg PO q8h | 10 mg/kg q8h | 600 mg per dose | Duration: 10–14 days; oral only q8h (not q12h) for children under 5 |
| Adolescents ≥12 years — all indications | 600 mg IV/PO q12h (or 400 mg PO q12h for uSSSI) | Adult dosing | 600 mg per dose | Use adult dosing schedule from age 12 |
Linezolid’s near-complete oral bioavailability is its defining pharmacokinetic advantage. Unlike vancomycin, which requires IV administration for systemic infections, linezolid can be stepped down from IV to oral without any dose adjustment, producing equivalent serum concentrations. This enables earlier hospital discharge and outpatient completion of therapy, significantly reducing healthcare costs and IV line-associated complications. Food does not affect the extent of absorption (though it may slightly delay the rate), so linezolid can be taken with or without food.
Pharmacology
Mechanism of Action
Linezolid is a synthetic oxazolidinone antibiotic that inhibits bacterial protein synthesis through a unique mechanism: it binds to the 23S ribosomal RNA of the 50S subunit, preventing formation of the 70S initiation complex required for translation. This site of action is distinct from that of other protein synthesis inhibitors (macrolides, aminoglycosides, tetracyclines), which is why cross-resistance with these classes is uncommon. Linezolid is primarily bacteriostatic against enterococci and staphylococci, but exhibits bactericidal activity against most streptococcal species. In addition to its antibacterial activity, linezolid is a weak, reversible, non-selective inhibitor of monoamine oxidase (MAO), which accounts for its interactions with serotonergic and adrenergic agents.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | Rapidly and completely absorbed; ~100% oral bioavailability; Tmax 1–2 h; food does not affect extent of absorption | IV-to-oral switch requires no dose change; enables outpatient oral therapy for serious infections |
| Distribution | Vd 40–50 L (approximately total body water); protein binding ~31%; good penetration into lung ELF, bone, muscle, fat, CSF, skin blister fluid | CSF penetration variable (reported ~70% of plasma in adult studies, but inconsistent in pediatric data per FDA PI); saliva-to-plasma ratio 1.2:1 |
| Metabolism | Non-enzymatic oxidation of morpholine ring to two inactive metabolites (PNU-142586, PNU-142300); not CYP450-mediated; may exhibit autoinhibition of metabolism | Minimal CYP-mediated drug interactions; no significant effect on CYP substrates (warfarin, phenytoin unaffected); metabolites may accumulate in severe renal impairment |
| Elimination | ~30% unchanged in urine; ~50% as metabolites in urine; t½ 5–7 h; ~30% removed by 3-hour haemodialysis session | No dose adjustment for renal impairment (parent drug clearance unchanged), but metabolite accumulation of unknown significance; dose after dialysis sessions |
Side Effects
Safety data from 2,046 adults in seven Phase 3 comparator-controlled trials (treatment up to 28 days). For uncomplicated SSTI, 25.4% of linezolid-treated patients experienced at least one drug-related adverse event compared with 19.6% of comparator-treated patients (FDA PI).
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Diarrhea | 3–11% | Ranges across indications; distinguish from C. difficile-associated diarrhea; linezolid itself may have activity against C. difficile |
| Headache | 1–11% | More common in pneumonia trials; usually mild and self-limiting |
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Nausea | 3–10% | More frequent with oral dosing; may be mitigated by taking with food |
| Vomiting | 1–4% | Usually mild; if persistent, may reflect lactic acidosis (check lactate) |
| Insomnia | ~3% | Possibly related to weak MAO inhibition |
| Constipation | ~2% | Non-specific |
| Rash | ~2% | Usually maculopapular; discontinue if signs of serious dermatologic reaction |
| Dizziness | ~2% | Non-specific; assess concurrent medications |
| Oral candidiasis | ~1% | Antibiotic-associated; manage with topical antifungals |
| Altered taste (dysgeusia) | ~1% | Usually resolves after completion of therapy |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Thrombocytopenia | 2.4% (trials); 15–50% (post-marketing, prolonged use) | Typically after 10–14 days; mean ~5 days in some studies | Monitor CBC weekly; higher risk with renal impairment, courses >14 days, and baseline low platelets; discontinue if significant decline; usually reversible within ~5 days of stopping |
| Anemia (including sideroblastic) | ~2–7% (duration-dependent) | Typically after 2–3 weeks | Monitor haemoglobin weekly; linezolid inhibits mitochondrial protein synthesis in mammalian cells; usually reversible on discontinuation |
| Peripheral neuropathy | Uncommon (<1% in short courses; higher with >28 days) | Usually after >28 days of therapy | May be irreversible; monitor for paraesthesias, numbness in extremities; discontinue promptly if symptoms develop |
| Optic neuropathy (vision loss, blurred vision, colour changes) | Rare (primarily with prolonged courses >28 days) | Usually after >28 days of therapy | Prompt ophthalmology referral if any visual symptoms; may be irreversible; discontinue linezolid immediately |
| Serotonin syndrome | Rare (primarily with concurrent serotonergic agents) | Hours to days after co-administration | Discontinue linezolid and serotonergic agent; supportive care; avoid concurrent SSRIs, SNRIs, triptans, meperidine, tramadol unless no alternatives exist |
| Lactic acidosis | Rare (prolonged courses) | Weeks into therapy | Suspect if recurrent nausea/vomiting, unexplained acidosis, or low bicarbonate; check lactate; discontinue linezolid |
| Hypoglycemia | Uncommon (postmarketing; in diabetic patients) | Any time during therapy | Monitor blood glucose in diabetic patients on insulin or oral hypoglycemics; may need dose reduction of diabetic medications |
| Hyponatremia / SIADH | Rare (postmarketing) | Variable | Monitor sodium in elderly and patients on diuretics; discontinue if symptomatic hyponatremia develops |
| Pancytopenia | Rare | Duration-dependent | Discontinue immediately; bone marrow recovery usually follows drug withdrawal |
Linezolid-induced myelosuppression (particularly thrombocytopenia) is the most clinically significant dose-limiting toxicity. In Phase 3 trials limited to 28 days, thrombocytopenia occurred in approximately 2.4% of patients. However, post-marketing studies consistently report higher rates (15–50%) in patients treated beyond 14 days, those with renal impairment, and those on haemodialysis. The mechanism involves inhibition of mitochondrial protein synthesis in mammalian cells, which affects haematopoietic precursor cells. Weekly CBC monitoring is essential for all patients, with more frequent monitoring for those with risk factors. Thrombocytopenia is usually reversible within approximately 5 days of discontinuation. For prolonged courses (as in MDR-TB), dose reduction to 300 mg daily has been used to mitigate myelosuppression while maintaining efficacy.
Drug Interactions
Linezolid is a weak, reversible, non-selective inhibitor of monoamine oxidase (MAO). This property drives its most clinically significant interactions. Unlike traditional MAOIs, linezolid’s MAO inhibition is reversible, but the risk of serotonin syndrome and hypertensive crises is real and well-documented. Linezolid is not metabolised by CYP450 enzymes and does not significantly inhibit or induce them, so pharmacokinetic interactions with CYP substrates such as warfarin and phenytoin are not expected.
Monitoring
- CBC with Differential & PlateletsBaseline, then weekly
RoutineEssential for detecting thrombocytopenia, anemia, and neutropenia. Particularly critical for patients receiving >2 weeks of therapy, those with renal impairment, those on haemodialysis, or those with pre-existing myelosuppression. Consider discontinuation if platelets drop below 100 × 109/L or decline >50% from baseline. - Visual Acuity & Colour VisionBaseline if course >28 days; monthly for prolonged courses
Trigger-basedOptic neuropathy is primarily a risk with courses exceeding 28 days. Promptly evaluate any new visual symptoms (blurred vision, colour vision changes, visual field defects). Refer to ophthalmology immediately if suspected. - Peripheral Neuropathy AssessmentAt each visit for courses >28 days
Trigger-basedAsk about numbness, tingling, burning pain in hands/feet at each assessment. Peripheral neuropathy may be irreversible; early detection and prompt discontinuation are critical to limiting damage. - Blood PressureMonitor if concurrent adrenergic agents
Trigger-basedMAO inhibitor activity may potentiate pressor responses. Monitor blood pressure if patient requires vasopressors, decongestants, or has uncontrolled hypertension. - Blood GlucoseClosely in diabetic patients
Trigger-basedPostmarketing cases of symptomatic hypoglycemia in patients on insulin or oral hypoglycemics. Monitor and adjust diabetes medications as needed. - Serum LactateIf recurrent nausea/vomiting or unexplained acidosis
Trigger-basedLactic acidosis is a rare but serious complication of prolonged linezolid therapy. Suspect if patient develops unexplained metabolic acidosis, recurrent GI symptoms, or low bicarbonate. - Serotonin Syndrome SignsContinuously if concurrent serotonergic agents
RoutineMonitor for agitation, confusion, tachycardia, hyperthermia, diaphoresis, tremor, myoclonus, hyperreflexia, and incoordination. Onset typically within hours to days of co-administration.
Contraindications & Cautions
Absolute Contraindications
- Known hypersensitivity to linezolid or any component of the formulation
- Concurrent use of MAOIs or use within 2 weeks of an MAOI — risk of hypertensive crisis and serotonin syndrome
Relative Contraindications (Specialist Input Recommended)
- Concurrent serotonergic agents (SSRIs, SNRIs, triptans, meperidine, tramadol) — use only when no alternative antibiotic is available; requires close monitoring and may necessitate withholding the serotonergic agent
- Uncontrolled hypertension, pheochromocytoma, carcinoid syndrome, thyrotoxicosis — MAO inhibition may exacerbate hypertensive episodes
- Pre-existing myelosuppression or thrombocytopenia — linezolid will further suppress bone marrow function; consider daptomycin or other alternatives
Use with Caution
- Renal impairment (especially severe / haemodialysis) — metabolites accumulate; increased thrombocytopenia risk; dose linezolid after dialysis sessions; monitor CBC more frequently
- Moderate to severe hepatic impairment — limited data for Child-Pugh C; use with caution and monitor
- Diabetic patients on insulin or oral hypoglycemics — risk of symptomatic hypoglycemia; monitor blood glucose closely
- Treatment duration >28 days — significantly increased risk of peripheral neuropathy, optic neuropathy, and lactic acidosis; require enhanced monitoring and clear clinical justification for extended courses
- Phenylketonuria (PKU) — oral suspension contains phenylalanine (20 mg per 5 mL); use tablets or IV formulation instead
In an investigator-led study comparing linezolid to vancomycin for catheter-related bloodstream infections (an unapproved indication), a mortality imbalance was observed with more deaths in the linezolid arm. The imbalance was primarily in patients infected with Gram-negative organisms, Gram-positive/Gram-negative mixed infections, or patients with no identified pathogen at baseline. Linezolid is not FDA-approved for catheter-related bloodstream infections or catheter-site infections.
The FDA issued a drug safety communication regarding the risk of serotonin syndrome when linezolid is combined with serotonergic psychiatric medications. If linezolid treatment is urgently needed and cannot be delayed, the serotonergic agent should be stopped and the patient monitored for signs and symptoms of serotonin syndrome for the duration of linezolid treatment, or until 24 hours after the last linezolid dose, whichever comes first. The serotonergic agent may be resumed 24 hours after the last dose of linezolid.
Patient Counselling
Purpose of Therapy
Linezolid is an antibiotic used to treat serious bacterial infections that are resistant to other antibiotics. It can be given through a vein (IV) or taken by mouth as a tablet or liquid, with no difference in effectiveness between these routes. It is important to complete the full course of treatment as prescribed, even if you feel better early.
How to Take
Tablets may be taken with or without food. If using the oral liquid, gently invert the bottle 3–5 times before each dose (do not shake vigorously). Use the measuring device provided to ensure accurate dosing. The liquid should be stored at room temperature and discarded 21 days after reconstitution.
Sources
- Zyvox (linezolid) — Full Prescribing Information. Pfizer Inc. Revised 2024. FDA Label (2024)Primary regulatory source for all FDA-approved indications, dosing, pharmacokinetics, adverse reactions, drug interactions (MAO-related), and warnings including mortality imbalance in catheter-related BSI.
- FDA Drug Safety Communication: Serious CNS reactions possible when linezolid (Zyvox) is given to patients taking certain psychiatric medications. October 2011. FDA.govSafety communication establishing protocols for managing serotonergic medication co-administration with linezolid.
- Liu C, Bayer A, Cosgrove SE, et al. Clinical practice guidelines by the Infectious Diseases Society of America for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children. Clin Infect Dis. 2011;52(3):e18–e55. doi:10.1093/cid/ciq146IDSA MRSA guideline positioning linezolid as an alternative to vancomycin for MRSA pneumonia and an option for MRSA SSTI and bone/joint infections.
- Conradie F, Diacon AH, Ngubane N, et al. Treatment of highly drug-resistant pulmonary tuberculosis. N Engl J Med. 2020;382(10):893–902. doi:10.1056/NEJMoa1901814Nix-TB trial establishing the bedaquiline-pretomanid-linezolid (BPaL) regimen for XDR-TB and treatment-intolerant MDR-TB, documenting high myelosuppression and neuropathy rates with prolonged linezolid.
- WHO consolidated guidelines on tuberculosis. Module 4: treatment — drug-resistant tuberculosis treatment, 2022 update. Geneva: WHO; 2022. WHOWHO guideline classifying linezolid as a Group A agent (to be included in all MDR-TB regimens) with dosing and safety monitoring recommendations.
- Wunderink RG, Niederman MS, Kollef MH, et al. Linezolid in methicillin-resistant Staphylococcus aureus nosocomial pneumonia: a randomized, controlled study. Clin Infect Dis. 2012;54(5):621–629. doi:10.1093/cid/cir895Randomized trial showing non-inferior clinical cure rates for linezolid versus vancomycin in MRSA nosocomial pneumonia, with potential advantages in per-protocol analysis.
- Shinabarger DL, Marotti KR, Murray RW, et al. Mechanism of action of oxazolidinones: effects of linezolid and eperezolid on translation reactions. Antimicrob Agents Chemother. 1997;41(10):2132–2136. doi:10.1128/AAC.41.10.2132Seminal mechanistic study demonstrating linezolid’s inhibition of 70S initiation complex formation at the 50S ribosomal subunit.
- De Vriese AS, Coster RV, Smet J, et al. Linezolid-induced inhibition of mitochondrial protein synthesis. Clin Infect Dis. 2006;42(8):1111–1117. doi:10.1086/501356Study establishing the mechanistic basis for linezolid-induced myelosuppression and lactic acidosis through mitochondrial protein synthesis inhibition.
- MacGowan AP. Pharmacokinetic and pharmacodynamic profile of linezolid in healthy volunteers and patients with Gram-positive infections. J Antimicrob Chemother. 2003;51(Suppl 2):ii17–ii25. doi:10.1093/jac/dkg248Comprehensive PK/PD review documenting oral bioavailability (~100%), protein binding (31%), Vd (30–50 L), tissue penetration, and metabolic pathway.
- Stalker DJ, Jungbluth GL. Clinical pharmacokinetics of linezolid, a novel oxazolidinone antibacterial. Clin Pharmacokinet. 2003;42(13):1129–1140. doi:10.2165/00003088-200342130-00004Definitive PK study establishing half-life (5–7 h), non-enzymatic metabolism, metabolite accumulation in renal impairment, and haemodialysis clearance (~30% in 3 h).
- Boak LM, Rayner CR, Grayson ML, et al. Clinical population pharmacokinetics and toxicodynamics of linezolid. Antimicrob Agents Chemother. 2014;58(4):2334–2343. doi:10.1128/AAC.01885-13Population PK study relating linezolid exposure (trough concentrations) to thrombocytopenia risk and establishing toxicodynamic thresholds for safety monitoring.
- Rubinstein E, Isturiz R, Standiford HC, et al. Worldwide assessment of linezolid’s clinical safety and tolerability: comparator-controlled Phase III studies. Antimicrob Agents Chemother. 2003;47(6):1824–1831. doi:10.1128/AAC.47.6.1824-1831.2003Pooled Phase 3 safety analysis (n=2,046) documenting adverse event rates, drug-related event incidence, and thrombocytopenia frequency across indications.