Linezolid

Mechanism of action

Linezolid (Linezolide) is a synthetic antibacterial agent, a representative of the oxazolidinone class. Its mechanism of action involves inhibiting bacterial protein synthesis. The drug selectively binds to the 50S ribosomal subunit of the bacterial cell, preventing the formation of the functional initiation complex required for translation.

In terms of its binding site (acting on the 50S subunit), linezolid belongs to the same category as macrolides, ketolides, lincosamides, and chloramphenicol, but differs in its chemical structure and the absence of cross-resistance.

Spectrum of activity

The drug has a narrow yet clinically vital spectrum of action, primarily targeting Gram-positive flora. Its key feature is high activity against polyresistant ("problematic") pathogens that standard beta-lactams cannot handle.

Susceptible flora includes:

• Staphylococcus aureus, including MRSA (methicillin-resistant Staphylococcus aureus). Linezolid is active against both nosocomial (hospital-acquired) and community-acquired strains that have developed resistance to oxacillin and methicillin.
• Penicillin-resistant strains of Streptococcus and Pneumococcus.
• VRE (vancomycin-resistant enterococci and staphylococci).

Indications for use

Linezolid is the drug of choice (along with the glycopeptide vancomycin) for treating severe infections caused by MRSA.

Furthermore, it is absolutely indispensable for infectious processes associated with vancomycin-resistant strains (VRE). In situations where glycopeptide-structure drugs (vancomycin, teicoplanin) prove ineffective due to pathogen mutations, linezolid remains one of the few available lines of defense.

Side effects and drug interactions

A crucial pharmacological feature of linezolid that is often overlooked is its ability to act as a non-selective reversible monoamine oxidase (MAO) inhibitor. This creates serious risks of dangerous drug interactions.

• When co-administered with drugs that affect monoamine and serotonin reuptake (e.g., antidepressants), the risk of severe neurological and cardiovascular complications critically increases.
• Possible reactions include severe headache, tachycardia (rapid heart rate), and a sharp rise in blood pressure (hypertensive crisis).
• The most formidable, life-threatening condition during such an interaction is serotonin syndrome.

Forms of release and prescription rules

The drug (one of the trade names is Zyvox) is available in forms for parenteral and oral administration, which is convenient for step-down therapy:

• Tablets: 0.6 g each. Administered orally at a dosage of 0.8–1.2 g/day, divided into 2 doses.
• Infusion solution: in 0.2% bags — 300 ml. Administered intravenously by drip infusion over 30–120 minutes.

Class and exam questions

What else to study on this topic

• Mechanisms of staphylococcal resistance (MRSA) to beta-lactam antibiotics
• Comparison of linezolid and glycopeptides (vancomycin, teicoplanin) in the treatment of MRSA infections
• Vancomycin-resistant enterococci (VRE): epidemiology and treatment strategies
• Serotonin syndrome: pathophysiology, clinical presentation, and emergency care
• MAO inhibitors: pharmacodynamics and significant drug interactions

Other topics in the «Drugs and Prescriptions» section

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