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?

Cmax/MIC Signup and view all the answers

In what condition might vancomycin absorption occur after oral administration?

Patients with pseudomembranous colitis Signup and view all the answers

Which of the following best describes the action of vancomycin?

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

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

Accumulation of the drug in the system Signup and view all the answers

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

Dalbavancin Signup and view all the answers

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

Area under the concentration time curve Signup and view all the answers

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

Fosfomycin Signup and view all the answers

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

125 mg every 6 hours Signup and view all the answers

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

Renal excretion Signup and view all the answers

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

4 to 6 hours Signup and view all the answers

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

400 Signup and view all the answers

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

Intramuscular Signup and view all the answers

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

Increased renal toxicity Signup and view all the answers

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

Hypotension Signup and view all the answers

How does vancomycin enter the central nervous system?

Direct injection into the cerebrospinal fluid is necessary Signup and view all the answers

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

Toxicity and nephrotoxicity Signup and view all the answers

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

10 mg/min 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.