Medical Pharmacology Chapter 35  Antibacterial Drugs

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Linezolid (Zyvox)

  • 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

primary reference: Linezolid (Zyvox): The Medical Letter, volume 42 (issued 1079); May 29, 2000.

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