How the dose is calculated
Linezolid clearance differs by age, so children under 12 need a higher per-kg total daily dose divided three times a day, while those 12 and older (and adults) use a lower per-kg dose divided twice daily. Oral and IV doses are considered equivalent because of linezolid's near-complete oral bioavailability.
Typical dosing by indication
| Indication | Dose | Frequency | Max |
|---|---|---|---|
| Under 12 years | 30 mg/kg/day | every 8h (3×/day) | 1800 mg/day |
| ≥12 years/adult | 20 mg/kg/day | every 12h (2×/day) | 1200 mg/day |
Linezolid is generally reserved for confirmed or strongly suspected resistant Gram-positive infections (MRSA, VRE) or as an alternative when first-line agents cannot be used — it is not a routine first-choice antibiotic.
Clinical use
- Linezolid covers resistant Gram-positive organisms including MRSA and vancomycin-resistant Enterococcus (VRE), making it valuable when first-line agents aren't options.
- Near-complete oral bioavailability allows straightforward IV-to-oral switching at the same dose once a patient is clinically improving.
- Prolonged use (typically beyond 2 weeks) carries a risk of reversible myelosuppression (thrombocytopenia, anaemia) — full blood counts should be monitored during extended courses.
- A weak monoamine oxidase inhibitor — carries a risk of serotonin syndrome when combined with SSRIs, SNRIs, or other serotonergic drugs; review the medication list carefully before prescribing.
Frequently asked questions
What is linezolid used for?
Linezolid treats serious infections caused by resistant Gram-positive bacteria, including MRSA (methicillin-resistant Staphylococcus aureus) and VRE (vancomycin-resistant Enterococcus), when other options aren't suitable.
Why is the linezolid dose different for younger children?
Children under 12 clear linezolid from their body faster than older children and adults, so they need a higher per-kg total daily dose divided three times a day to maintain adequate drug levels.
Can linezolid be switched from IV to tablets at the same dose?
Yes — linezolid has near-complete oral bioavailability, so the oral dose is generally the same as the IV dose, allowing a straightforward switch once a patient can take oral medication.
Does linezolid interact with antidepressants?
Yes — it's a weak monoamine oxidase inhibitor and can cause serotonin syndrome when combined with SSRIs, SNRIs, or other serotonergic medications. Review the full medication list before prescribing.
References
- British National Formulary for Children (BNFc) — Linezolid.
- American Academy of Pediatrics Red Book — Linezolid.
- Liu C, et al. Clinical Practice Guidelines for MRSA Infections in Adults and Children (IDSA). Clin Infect Dis. 2011.