# Linezolid: veterinary dose and monograph

> Linezolid is a veterinary antibiotic. An oxazolidinone antibiotic and a critical LAST-RESORT agent for serious infections caused by multidrug-resistant GRAM-POSITIVE bacteria — methicillin-resistant staphylococci (MRSA/MRSP) and vancomycin-resistant enterococci (VRE). Indications include documented MRSA / MRSP infection with no other option; vancomycin-resistant enterococcal infection; serious resistant Gram-positive infection (culture-confirmed, no alternative). This monograph lists 4 reference doses for dogs and cats, each with route, frequency and source.

Source: https://vetmasterji.com/drugs/linezolid · Last reviewed: 2026-10-01

## At a glance

- **Drug class:** Antibiotic
- **Also known as:** Zyvox, Linospan, Lizolid
- **Species with doses:** Dogs and Cats
- **General dose range:** 10 mg/kg PO q8–12h — check the species tables for the indication
- **Routes:** PO
- **Last reviewed:** 1 October 2026

## Indications

- Documented MRSA / MRSP infection with no other option
- Vancomycin-resistant enterococcal infection
- Serious resistant Gram-positive infection (culture-confirmed, no alternative)

## Linezolid dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

### Dogs

*Linezolid doses for dogs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Resistant Gram-positive infection | 10 mg/kg | PO | q12h | — |
| Nocardiosis unresponsive to standard therapy | 8–20 mg/kg | PO | q12h | — |

- Resistant Gram-positive infection: Papich 5e: 10 mg/kg PO or IV q12h (oral bioavailability ≈ IV). Reserve for documented MRSP/MRSA or VRE with no alternative; monitor CBC on longer courses. Plumb’s 10e p.764 (dogs/cats, extra-label): multidrug-resistant infections 10 mg/kg PO every 8 to 12 hours; may be given IV at the same dose.
- Nocardiosis unresponsive to standard therapy: Plumb’s 10e p.764 (dogs/cats, extra-label): 8–20 mg/kg PO every 12 hours.

### Cats

*Linezolid doses for cats*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Resistant Gram-positive infection | 10 mg/kg | PO | q12h | — |
| Nocardiosis unresponsive to standard therapy | 8–20 mg/kg | PO | q12h | — |

- Resistant Gram-positive infection: Papich 5e (dogs and cats): 10 mg/kg PO or IV q12h. Plumb’s 10e p.764 (dogs/cats, extra-label): 10 mg/kg PO every 8 to 12 hours, or IV at the same dose. Reserve for resistant infections; monitor CBC.
- Nocardiosis unresponsive to standard therapy: Plumb’s 10e p.764 (dogs/cats, extra-label): 8–20 mg/kg PO every 12 hours.

## Contraindications

Routine use (a reserved human last-resort drug — major stewardship concern). Concurrent serotonergic drugs (SSRIs, tramadol, mirtazapine, MAOIs, amitraz) — serotonin syndrome. Pre-existing significant myelosuppression. Known hypersensitivity. Prolonged courses (cumulative marrow/optic/peripheral neurotoxicity).

## Adverse effects

- Myelosuppression — thrombocytopenia, anaemia, neutropenia (dose/duration-related)
- GI upset (vomiting, diarrhoea)
- Serotonin syndrome with serotonergic co-medication (weak MAOI)
- Peripheral / optic neuropathy and lactic acidosis with prolonged use

## Drug interactions

- Serotonergic drugs (SSRIs, tramadol, mirtazapine, MAOIs, amitraz): serotonin syndrome (linezolid is a weak MAOI) — avoid
- Sympathomimetics / tyramine: potentiated pressor effect
- Other myelosuppressive drugs: additive marrow suppression

## Pregnancy and lactation

Limited data; reserve for life-threatening resistant infection where benefit outweighs risk.

## Monitoring

- CBC (PLATELETS especially) weekly — myelosuppression is dose/duration-related
- Culture confirming a no-alternative resistant Gram-positive (mandatory stewardship)
- Serotonergic co-medications (avoid); neurologic/visual signs on long courses
- Documented justification / stewardship records

## Toxicity and overdose

Dose- and duration-dependent MYELOSUPPRESSION (thrombocytopenia first, then anaemia/neutropenia) is the key toxicity — usually reversible on stopping. Prolonged courses (weeks) risk peripheral and optic neuropathy and lactic acidosis. Serotonin syndrome can occur with serotonergic drugs. Stewardship "toxicity": eroding a critical human reserve drug.

Management: No specific antidote. Discontinue; supportive care, monitor and support CBC (transfusion if severe cytopenia). Manage serotonin syndrome (cyproheptadine, cooling, supportive care). Effects on marrow generally reverse after stopping.

## Clinical pearls

- A genuine last-resort drug — reserve strictly for culture-confirmed MRSA/MRSP/VRE with no alternative (a vital human antibiotic; One-Health stewardship)
- Oral and IV doses are interchangeable (near-100% bioavailability) — convenient but not a reason to use it casually
- Monitor the PLATELET count (and CBC) weekly — thrombocytopenia is the commonest dose-limiting effect
- It is a weak MAOI — avoid serotonergic drugs (tramadol, SSRIs, mirtazapine, amitraz) to prevent serotonin syndrome

## Mechanism of action

Binds the 23S rRNA of the 50S bacterial ribosomal subunit at a unique site, preventing formation of the 70S initiation complex and blocking the very first step of protein synthesis — bacteriostatic against staphylococci/enterococci (bactericidal against some streptococci). Its novel binding site means little cross-resistance with other classes. It also weakly and reversibly inhibits monoamine oxidase, the basis of serotonin-syndrome interactions.

## Formulations and products

- 600 mg tablet
- IV infusion 2 mg/mL (300 mL bag)
- Oral suspension 20 mg/mL
- Zyvox — 600 mg tablet; 2 mg/mL IV; 20 mg/mL suspension, Tablet / IV / suspension (human-label)
- Linospan / Lizolid — 600 mg tablet, Tablet (human-label)

## Storage

Tablets/suspension/IV: 15–30 °C, protect from light; IV bags protect from light, do not freeze.

## Before you use this dose

> **Caution:** Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

## Other antibiotics

- [Gamithromycin](https://vetmasterji.com/drugs/gamithromycin)
- [Gentamicin](https://vetmasterji.com/drugs/gentamicin)
- [Levofloxacin](https://vetmasterji.com/drugs/levofloxacin)
- [Lincomycin](https://vetmasterji.com/drugs/lincomycin)
- [Marbofloxacin](https://vetmasterji.com/drugs/marbofloxacin)
- [Meropenem](https://vetmasterji.com/drugs/meropenem)
- [Minocycline](https://vetmasterji.com/drugs/minocycline)
- [Mupirocin](https://vetmasterji.com/drugs/mupirocin)

## Frequently asked questions

### What is the dose of Linezolid for dogs?

Reference doses for Linezolid in dogs: 10 mg/kg PO q12h (Resistant Gram-positive infection); 8–20 mg/kg PO q12h (Nocardiosis unresponsive to standard therapy). Confirm against the label and the patient before use.

### What is the dose of Linezolid for cats?

Reference doses for Linezolid in cats: 10 mg/kg PO q12h (Resistant Gram-positive infection); 8–20 mg/kg PO q12h (Nocardiosis unresponsive to standard therapy). Confirm against the label and the patient before use.

### When should Linezolid not be used?

Routine use (a reserved human last-resort drug — major stewardship concern). Concurrent serotonergic drugs (SSRIs, tramadol, mirtazapine, MAOIs, amitraz) — serotonin syndrome. Pre-existing significant myelosuppression. Known hypersensitivity. Prolonged courses (cumulative marrow/optic/peripheral neurotoxicity).

### What are the side effects of Linezolid in animals?

Myelosuppression — thrombocytopenia, anaemia, neutropenia (dose/duration-related); GI upset (vomiting, diarrhoea); Serotonin syndrome with serotonergic co-medication (weak MAOI); Peripheral / optic neuropathy and lactic acidosis with prolonged use.

## Sources

- Plumb's Veterinary Drug Handbook
- Merck Veterinary Manual, 11th edition
- Papich, Papich Handbook of Veterinary Drugs, 5th edition

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VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.