Chapter 38: Part 2 Antibiotics

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Questions and Answers

What is the primary mechanism of action of aminoglycosides?

Prevent nucleic acid synthesis

Prevent protein synthesis (correct)

Inhibit cell wall synthesis

Enhance cell permeability

Which of the following statements regarding VRE is true?

VRE is resistant only to beta-lactam antibiotics.

VRE can be effectively treated with all existing antibiotics.

VRE is often found in urinary tract infections. (correct)

VRE is exclusively associated with respiratory infections.

Which of the following best describes MRSA?

A type of antimicrobial resistant to all aminoglycosides.

A gram-negative organism that causes respiratory infections.

A strain of staphylococcus aureus resistant to methicillin. (correct)

A strain of staphylococcus aureus that is only present in hospitals.

Aminoglycosides are contraindicated for which of the following routes of administration for most patients?

Oral Signup and view all the answers

What is a common adverse effect associated with aminoglycosides?

Nephrotoxicity Signup and view all the answers

What is the classification of organisms producing extended-spectrum beta-lactamases (ESBLs)?

Multidrug-resistant organisms Signup and view all the answers

Which of the following is an important consideration when using aminoglycosides in treatment?

They often require synergistic use with other antibiotics. Signup and view all the answers

Why is the administration route important when considering aminoglycosides?

Only parenteral administration is effective. Signup and view all the answers

Which of the following antibiotics is used specifically for skin and skin structure infections caused by MRSA?

Dalbavancin Signup and view all the answers

What serious adverse effect may occur when administering colistimethate by inhalation?

Acute respiratory failure Signup and view all the answers

Which antibiotic is specifically indicated for treating infections caused by vancomycin-resistant Enterococcus faecium?

Linezolid Signup and view all the answers

What potential interaction should be considered when prescribing linezolid?

Interaction with SSRIs Signup and view all the answers

Which mechanism of action is primarily associated with daptomycin?

Disrupts cell membrane potential Signup and view all the answers

What type of infections can metronidazole effectively treat?

Intraabdominal and gynecologic infections Signup and view all the answers

Which of the following drugs may cause Clostridioides difficile infection?

Clindamycin Signup and view all the answers

Which antibiotic class does Lefamulin belong to?

Pleuromutilins Signup and view all the answers

What are the key significant adverse effects associated with aminoglycosides?

Nephrotoxicity and ototoxicity Signup and view all the answers

In therapeutic drug monitoring of aminoglycosides, what do the peak and trough levels indicate?

Peak indicates the highest drug level, and trough indicates the lowest. Signup and view all the answers

What is the primary reason for monitoring drug levels of aminoglycosides in patient's serum?

To prevent adverse effects and toxicity Signup and view all the answers

Which of the following best describes the postantibiotic effects of aminoglycosides?

They continue to inhibit bacterial growth even after serum levels have declined. Signup and view all the answers

Which statement about the minimum inhibitory concentration (MIC) is true regarding aminoglycosides?

MIC is crucial for determining the effectiveness of aminoglycosides in treatment. Signup and view all the answers

What potential risk can occur due to drug interactions with aminoglycosides?

Decreased renal clearance leading to higher toxicity risk Signup and view all the answers

Which of these adverse effects are typically associated with aminoglycosides, aside from nephrotoxicity and ototoxicity?

Superinfections and vertigo Signup and view all the answers

What mechanism is responsible for resistance to aminoglycosides?

Mutations in bacterial genes leading to decreased drug uptake or increased inactivation Signup and view all the answers

Study Notes

Antibiotics Part 2

Multidrug-resistant organisms (MDROs) are resistant to one or more classes of antimicrobial drugs.
Examples of MDROs include:
- Methicillin-resistant Staphylococcus aureus (MRSA)
- Vancomycin-resistant Enterococcus (VRE)
- Organisms producing extended-spectrum beta-lactamases (ESBLs)
MRSA is increasingly common in the community setting and is resistant to most available antibiotics. Community spread of MRSA is an increasing concern.
Approximately half of community staphylococcal infections involve MRSA.
Newer antibiotics have been developed to treat VRE and MRSA.
VRE is often found in urinary tract infections.

Aminoglycosides Overview

Origin: Natural and semisynthetic antibiotics from the Streptomyces genus
Administration: Poor oral absorption; no oral forms (neomycin is an exception)
Potency: Very potent, but with significant toxicities
Mechanism of Action: Bactericidal; inhibits protein synthesis

Common Aminoglycosides

Gentamicin (brand name: Neo-Fradin)
Tobramycin (brand name: TOBI)
Amikacin

Aminoglycosides: Indications

Gram-Negative Infections: Effective against organisms such as Pseudomonas, Escherichia coli, Proteus, Klebsiella, and Serratia.
Gram-Positive Resistance: Used for infections resistant to other antibiotics.
Synergistic Effects: Often used with other antibiotics (such as beta-lactams or vancomycin) to enhance effectiveness.
Parenteral Administration: Common route of administration due to poor GI absorption.
Inhalation Therapy: Also used for lung infections
Neomycin Exception: Given orally to decontaminate GI tract before surgery

Aminoglycosides: Adverse Effects

Nephrotoxicity: Renal damage
Drug Level Monitoring: Essential to prevent toxicity
Ototoxicity: Auditory and vestibular impairment.
Minimum Inhibitory Concentration (MIC): Important for treatment
Significant Adverse Effects: Ototoxicity and nephrotoxicity are major concerns
Other Adverse Effects: Headache, paresthesia, fever, superinfections, vertigo, skin rash, and dizziness are also possible.

Aminoglycosides: Therapeutic Drug Monitoring

Serum Levels: Measured to prevent toxicity
Peak and Trough: Peak is the highest drug level and trough is the lowest to ensure adequate renal clearance without toxicity.

Aminoglycosides: Therapeutic Drug Monitoring (Cont'd)

Postantibiotic Effects: Aminoglycosides continue to inhibit bacterial growth after serum concentrations decline.
Resistance: Resistance to aminoglycosides can develop due to mutations in bacterial genes that lead to decreased drug uptake or increased inactivation.
Drug Interactions: Aminoglycosides can interact with other drugs (such as loop diuretics and neuromuscular blocking agents) potentially increasing the risk of adverse effects.

Quinolones Overview

Fluoroquinolones: Another class of antibiotics
Oral Absorption: Excellent oral absorption
Antacid Impact: Absorption reduced by antacids
Spectrum of Activity: Effective against Gram-negative and some Gram-positive organisms

Common Quinolones

Ciprofloxacin (brand name: Cipro)
Norfloxacin (brand name: Noroxin)
Levofloxacin (brand name: Levaquin)
Moxifloxacin (brand name: Avelox)

Quinolones: Mechanism of Action

Bactericidal: Quinolones are bactericidal antibiotics
DNA Alteration: Quinolones alter bacterial DNA, causing bacterial death.
Human DNA: Quinolones do not affect human DNA.
Bacterial Resistance: Resistance to quinolones is a growing concern

Quinolones: Indications

Gram-Negative Infections: Effective against Pseudomonas spp.
Infections: Treat complicated urinary tract, respiratory, bone and joint, GI, and sexually transmitted infections.
Anthrax: Ciprofloxacin is used for anthrax treatment

Quinolones: Interactions

Oral Quinolones: Antacids, calcium, magnesium, iron, or zinc, or sucralfate interfere with absorption
Dairy Products: Interfere with absorption
Enteral Tube Feedings: Also interfere with absorption
Other Interactions: Probenecid, nitrofurantoin, and oral anticoagulants
Additional Interactions: Must be monitored for specific drug interactions unique to each antibiotic class

Quinolones: Adverse Effects

CNS: Headache, dizziness, insomnia, depression, restlessness, convulsions
GI: Nausea, vomiting, diarrhea, constipation, thrush, increased liver function study results, others
Cardiac: Prolonged QT interval
Integumentary: Rash, pruritus, urticaria, flushing
Other: Ruptured tendons, tendonitis, fever, chills, blurred vision, tinnitus

Miscellaneous Antibiotics

Clindamycin (Cleocin): Used for bacterial infections
Linezolid (Zyvox): For serious bacterial infections
Metronidazole (Flagyl): Treat anaerobic bacterial infections
Nitrofurantoin (Macrodantin, Furadantin): Treat urinary tract infections
Pleuromutilins: Lefamulin (Xenleta) and Retapamulin (Altabax)

Clindamycin Details

Indications: Chronic bone, genitourinary, intra-abdominal, and other serious infections.
Adverse Effects: Pseudomembranous colitis (Clostridioides difficile diarrhea/infection)
Drug Interactions: Potential interaction with vecuronium

Daptomycin (Cubicin)

Lipopeptide Class: Daptomycin is the only drug in this class
Mechanism of Action: Binds to gram-positive cells in a calcium-dependent process; disrupting the cell membrane

Colistinmethate (Coly-Mycin)

Polypeptide antibiotic, that disrupts the bacterial membrane of certain susceptible gram-negative strains.
Serious adverse effects can occur.
Inhalation administration can lead to serious respiratory problems.

Dalbavancin (Dalvance)

Lipoglycopeptide antibiotic
Effective against MRSA
Long Half-Life (once weekly dosing)
Indications: Skin and skin structure infections caused by susceptible gram-positive organisms

Linezolid (Zyvox)

New Class: Oxazolidinones
Indications: Treats vancomycin-resistant Enterococcus faecium, hospital-acquired, and skin structure infections, including those with MRSA.
Adverse Effects: Hypotension, serotonin syndrome (if taken with SSRIs), and reactions to tyramine-containing foods.

Metronidazole (Flagyl)

Indications: Intra-abdominal and gynecologic infections
Anaerobic Organisms: Used to treat anaerobic infections and protozoa infections
Drug Interactions: Has several potential drug interactions

Nitrofurantoin (Macrodantin)

Indications: Primarily UTI's caused by E. coli, S. aureus, Klebsiella, and Enterobacter.
Considerations: Use carefully if renal function is impaired. Drug concentrates in the urine.

Quinupristin-dalfopristin (Synercid)

Combination antibiotic (30:70) of quinupristin and dalfopristin
Mechanism of action: synergistic
Indications: Bacteremia and infections caused by VRE.

Telavancin (Vibativ)

Lipoglycopeptide antibiotic
Treats skin, skin structure infections and pneumonia from gram-positive organisms
Adverse effects: Renal toxicity, infusion-related reactions, and QT prolongation

Vancomycin Overview

Treatment of Choice: Standard treatment of methicillin-resistant Staphylococcus aureus (MRSA) and other gram-positive infections
Oral Vancomycin: Indicated for antibiotic-induced colitis (C. difficile) and staphylococcal enterocolitis.

Vancomycin Details

Red Man Syndrome: Flushing or itching of the head, neck, face, and upper trunk
Neuromuscular Blockers: Additive neuromuscular blocking effects can occur if given with other neuromuscular blockers
Infusion Rate: Administered over 60 minutes to minimize risk of hypotension
Blood Levels: Monitor to ensure therapeutic efficacy.

Nursing Implications

Drug Allergies: Assess for drug allergies before beginning therapy
Hepatic, Renal, Cardiac Function: Assess function before starting therapy
Patient Health History: Thorough history, including immune status
Drug Interactions: Assess potential drug interactions
Culture Collection: Obtain cultures before starting antibiotics
Medication Adherence: Educate patients to take antibiotics as prescribed
Superinfection Assessment: Monitor for signs of superinfection
Medication Verification: Verify medication names to prevent errors
Adverse Effects and Interactions: Assess for specific adverse effects and drug interactions associated with each antibiotic.

Monitoring for Therapeutic Effects

Signs of Improvement: Monitor signs and symptoms of infection and return to normal vital signs
Negative Cultures: Ensure negative cultures and sensitivity tests for specific outcomes
Observe for: Disappearance of fever, lethargy, drainage, and redness

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Description

This quiz covers the pharmacological aspects of aminoglycosides, focusing on their mechanisms of action, administration routes, and associated adverse effects. Additionally, it addresses critical information about MRSA and VRE, providing insights relevant for healthcare professionals and students in pharmacology.