Overview

• Linezolid (Zyvox) should be used only for well-documented, serious vancomycin (Vancocin) resistant enterococcal infections

• New antibiotic class: oxazolidinones

• Management for infections caused by:

  • Vancomycin (Vancocin)-resistant Enterococcus faecium

  • Nosocomial & community-acquired Staphylococcus aureus pneumonia

  • Nosocomial & community acquired danazol (Donocrine)-susceptible Streptococcus pneumoniae

  • Skin & skin-structure infections

Two formulations FDA approved for treatment of vancomycin (Vancocin)-resistant enterococci:

• linezolid (Zyvox)--oral & parenteral use

• quinupristin/dalfopristin (Synercid) -- parenteral use only

Antibacterial characteristics

• Inhibits bacterial ribosomal-mediated protein synthesis

• Bacteria static against streptococci

• Activity profile:

  •  Linezolid (Zyvox): effective against both E. faecium and Enterococcus faecalis {quinupristin/dalfopristin (Synercid): active against vancomycin (Vancocin)-resistant E. faecium but not Enterococcus faecalis}

  •  Linezolid (Zyvox):

    •  Active against staphylococci, including methicillin (Staphcillin) resistance Staphylococcus aureus & methicillin (Staphcillin) resistance Staphylococcus epidermidis

    • Active against  penicillin-resistant pneumococci & Staphylococcus aureus with intermediate susceptibility vancomycin (Vancocin)

  •  No clinical useful gram-negative activity

Pharmacokinetics:

• Following oral administration:  rapid/complete absorption from  gastrointestinal tract

• Partial hepatic metabolism

• Urinary excretion

 Side/Adverse Effects

• Well-tolerated

• Most-common adverse effects: gastrointestinal (nausea, diarrhea, vomiting)

• With prolonged use: reversible thrombocytopenia

  • For treatment > 2 weeks, platelet count monitoring is recommended

• Linezolid (Zyvox) oral suspension contains phenylalanine, contraindicated in patients with  phenylketonuria

Drug-Drug Interactions

• Linezolid (Zyvox)-weak MAO inhibitor (nonselective)

• Patients should avoid  tyramine-rich foods

• Cautious use with linezolid (Zyvox) in combination with:

  •  pseudoephedrine

  •  phenylpropanolamine

  •  serotonin selective reuptake inhibitors (SSRIs)

  • possibly other antidepressants

• No effect on cytochrome P450 enzyme metabolizing system