8. Glycopeptides and Cell Wall Inhibitors
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Questions and Answers

Which of the following antibiotics is classified as a 1st generation glycopeptide?

  • Dalbavancin
  • Vancomycin (correct)
  • Oritavancin
  • Telavancin
  • Which of the following is NOT a characteristic of glycopeptides?

  • Bactericidal action
  • Effective against Gram-negative bacteria (correct)
  • Large molecular weight
  • Hydrophilic nature
  • What does the term 't > MIC' represent in antibiotic pharmacodynamics?

  • The maximum concentration achieved by the antibiotic
  • The duration drug concentration is above the minimum inhibitory concentration (correct)
  • The time needed for the drug to reach peak concentration
  • The cumulative effect of the antibiotic over 24 hours
  • Which parameter is used for concentration-dependent antibiotics?

    <p>Cmax/MIC</p> Signup and view all the answers

    In what condition might vancomycin absorption occur after oral administration?

    <p>Patients with pseudomembranous colitis</p> Signup and view all the answers

    Which of the following best describes the action of vancomycin?

    <p>It does not penetrate well into Gram-negative bacterial cell membranes</p> Signup and view all the answers

    What is the primary issue in administering vancomycin orally in patients with renal impairment?

    <p>Accumulation of the drug in the system</p> Signup and view all the answers

    Which of the following compounds is classified as a 2nd generation glycopeptide?

    <p>Dalbavancin</p> Signup and view all the answers

    What does AUC stand for in the context of antibiotic pharmacokinetics?

    <p>Area under the concentration time curve</p> Signup and view all the answers

    Which of the following is an example of an other cell wall inhibitor?

    <p>Fosfomycin</p> Signup and view all the answers

    What is the recommended initial oral dose of vancomycin for C. difficile associated diarrhea?

    <p>125 mg every 6 hours</p> Signup and view all the answers

    What is the primary method of elimination for vancomycin from the body?

    <p>Renal excretion</p> Signup and view all the answers

    What is the elimination half-life of vancomycin in patients with normal renal function?

    <p>4 to 6 hours</p> Signup and view all the answers

    What is the target AUC/MIC ratio for achieving clinical effectiveness with vancomycin?

    <p>400</p> Signup and view all the answers

    Which of the following routes should not be used for administering vancomycin?

    <p>Intramuscular</p> Signup and view all the answers

    What is the result of vancomycin accumulation in patients with impaired renal function?

    <p>Increased renal toxicity</p> Signup and view all the answers

    Which adverse effect could occur from rapid intravenous infusion of vancomycin?

    <p>Hypotension</p> Signup and view all the answers

    How does vancomycin enter the central nervous system?

    <p>Direct injection into the cerebrospinal fluid is necessary</p> Signup and view all the answers

    What is a potential risk when vancomycin trough levels exceed 20 µg/mL?

    <p>Toxicity and nephrotoxicity</p> Signup and view all the answers

    What is the maximum rate at which intravenous vancomycin should be infused to minimize adverse effects?

    <p>10 mg/min</p> Signup and view all the answers

    Study Notes

    Glycopeptides and Other Cell Wall Inhibitors

    • Glycopeptides are a class of antibiotics that originated from bacteria found in plants and soil.
    • Glycopeptides act as bactericidal agents against Gram-positive bacteria.
    • Glycopeptides have large molecular weight and a high affinity for water, making them unable to pass through the cell membranes of Gram-negative bacteria.
    • First-generation glycopeptide antibiotics:
      • Vancomycin
      • Teicoplanin
    • Second-generation glycopeptide antibiotics (also known as Lipoglycopeptides):
      • Telavancin
      • Oritavancin
      • Dalbavancin
    • Other cell wall inhibitors:
      • Fosfomycin

    Antibiotics: Time vs. Concentration Dependent Activity

    • The effectiveness of antibiotics is determined by a combination of pharmacokinetic (PK) parameters and bacterial sensitivity (MIC).
    • The Cmax/MIC ratio is a key factor for concentration-dependent antibiotics - here, the maximum antibiotic concentration (Cmax) is divided by the MIC.
    • The t > MIC ratio is key for time-dependent antibiotics - this refers to the length of time during which the drug concentration remains above the MIC within a dosing interval.
    • The AUC/MIC ratio is also important to consider. This is the area under the curve (AUC) of a concentration-time graph measured over a 24-hour period, divided by the MIC. The AUC represents the overall exposure to the antibiotic.

    Vancomycin: Therapeutic Guidelines

    • Vancomycin is poorly absorbed when administered orally.
    • Oral vancomycin may be absorbed in patients with colitis, potentially leading to vancomycin accumulation in those with renal impairment.
    • Oral vancomycin is used to treat Clostridium difficile associated diarrhea (CDAD), with guidelines suggesting an initial dose of 125 mg every 6 hours.
    • Though oral absorption is limited, oral vancomycin can reach concentrations significantly higher than the MIC for C. difficile at the site of action.
    • Vancomycin is usually administered via intravenous (IV) infusion over 60 minutes at a rate of 10 mg/min or greater to reduce the risk of adverse reactions.
    • Intravenous administration can lead to various reactions, including:
      • Red-man/red-neck syndrome
      • Shock
      • Cardiac arrest
      • Wheezing
      • Muscle and chest pain
    • Vancomycin is not recommended for intramuscular (IM) administration due to its potential to irritate tissue and cause necrosis at the injection site.

    Vancomycin: Pharmacokinetic Properties

    • Vancomycin poorly penetrates lung tissue.
    • Nebulized vancomycin is currently undergoing research for potential therapeutic applications.
    • Vancomycin does not enter the central nervous system in substantial amounts when given intravenously, requiring higher steady-state peak and trough concentrations.
    • Direct administration into the cerebrospinal fluid may be necessary.
    • The elimination half-life of vancomycin is 4 to 6 hours in individuals with normal renal function.
    • Vancomycin is predominantly eliminated through the kidneys, with approximately 80% excreted in urine within the first 24 hours.
    • Dosage adjustments are crucial in individuals with impaired renal function to avoid accumulation.
    • Vancomycin-induced renal damage has been reported.

    Vancomycin: Trough Concentration and Efficacy

    • Steady-state vancomycin trough levels typically fall between 15-20 µg/mL.
    • Trough levels above 20 µg/mL are associated with a higher incidence of nephrotoxicity.
    • Vancomycin exhibits concentration-independent activity, making the AUC/MIC ratio the primary predictor of efficacy.
    • Research suggests an AUC/MIC ratio of 400 is a target for achieving clinical effectiveness with vancomycin.

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    Description

    Test your knowledge on glycopeptides and their role as antibiotics. This quiz covers the characteristics, examples, and mechanisms involved in their effectiveness against Gram-positive bacteria. Additionally, explore the pharmacokinetic aspects influencing antibiotic activity.

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