1. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Chapter 39
Antibiotics Part 2
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2. Antibiotic Therapy: Concepts
Multidrug resistance
Therapeutic drug monitoring
Minimum inhibitory concentration (MIC)
Time-dependent killing
Concentration-dependent killing
Once-daily dosing vs. multidaily dosing
Peak and trough blood levels
Synergistic effects
Postantibiotic effect (PAE)
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3. Multidrug-Resistant Organisms
Organisms that are resistant to one or more classes of antimicrobial drugs
Methicillin-resistant Staphylococcus aureus (MRSA)
Vancomycin-resistant Enterococcus (VRE)
Organisms producing extended-spectrum beta-lactamases (ESBLs)
Organisms producing Klebsiella pneumoniae carbapenemase (KPC)
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4. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Aminoglycosides
Natural and semisynthetic
Produced from Streptomyces
Poor oral absorption; no PO forms (exception neomycin)
Very potent antibiotics with serious toxicities
Bactericidal; prevent protein synthesis
Kill mostly gram-negative bacteria; some gram-positive
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5. Aminoglycosides (cont’d)
gentamicin
neomycin (Neo-fradin)
tobramycin (TOBI)
amikacin
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6. Aminoglycosides: Indications
Used to kill gram-negative bacteria, such as Pseudomonas spp., Escherichia coli, Proteus spp., Klebsiella spp., Serratia spp.
Often used in combination with other antibiotics for synergistic effects
Used for certain gram-positive infections that are resistant to other antibiotics
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7. Aminoglycosides: Indications (cont’d)
Aminoglycosides are poorly absorbed through the GI tract, and given parenterally
Exception: neomycin
Given orally to decontaminate the GI tract before surgical procedures
Also used as an enema for this purpose
Used to treat hepatic encephalopathy
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8. Aminoglycosides: Adverse Effects
Cause serious toxicities
Nephrotoxicity (renal damage)
Ototoxicity (auditory impairment and vestibular impairment [eighth cranial nerve])
Must monitor drug levels to prevent toxicities
Minimum inhibitory concentration (MIC)
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9. Aminoglycosides: Adverse Effects (cont’d)
Ototoxicity and nephrotoxicity are the most significant
Headache
Paresthesia
Fever
Superinfections
Vertigo
Skin rash
Dizziness
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10. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Quinolones
Also called fluoroquinolones
Excellent oral absorption
Absorption reduced by antacids
Effective against gram-negative organisms and some gram-positive organisms
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11. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Quinolones (cont’d)
ciprofloxacin (Cipro)
norfloxacin (Noroxin)
levofloxacin (Levaquin)
moxifloxacin (Avelox)
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12. Quinolones: Mechanism of Action
Bactericidal
Alter DNA of bacteria, causing death
Do not affect human DNA
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13. Quinolones: Indications
Gram-negative bacteria such as Pseudomonas
Complicated urinary tract, respiratory, bone and joint, GI, skin, and sexually transmitted infections
Anthrax (ciproflaxin)
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14. Classroom Response Question
During intravenous quinolone therapy in an 88-year-old patient, which potential problem is of most concern when assessing for adverse effects?
Hepatotoxicity
Rhabdomyolysis
Tendon rupture
Nephrotoxicity
Correct answer: C
Rationale: A black box warning is required by the U.S. Food and Drug Administration for all quinolones because of the increased risk of tendonitis and tendon rupture with use of the drugs. This effect is more common in elderly patients, patients with renal failure, and those receiving concurrent glucocorticoid therapy (e.g., prednisone).
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15. Quinolones: Adverse Effects
Body System Adverse Effects CNS Headache, dizziness, insomnia, depression, restlessness, convulsions GI Nausea, vomiting, diarrhea, constipation, thrush, increased liver function studies, others Cardiac Prolonged QT interval
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16. Quinolones: Adverse Effects (cont’d)
Body System Adverse Effects
Integumentary Rash, pruritus, urticaria, flushing
Other Ruptured tendons,* tendonitis,* fever, chills, blurred vision, tinnitus
*Black box warning: Increased risk of tendonitis and tendon rupture
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17. Miscellaneous Antibiotics
clindamycin (Cleocin)
linezolid (Zyvox)
metronidazole (Flagyl)
nitrofurantoin (Macrodantin)
quinupristin/dalfopristin (Synercid)
daptomycin (Cubicin)
vancomycin (Vancocin)
colistimethate (Coly-Mycin)
telavancin (Vibativ)
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18. Miscellaneous Antibiotics (cont’d)
clindamycin (Cleocin)
Used for chronic bone infections, GU infections, intraabdominal infections, other serious infections
May cause pseudomembranous colitis (also known as antibiotic-associated colitis, Clostridium difficile diarrhea, or C. difficile infection)
Potential interaction with vecuronium
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19. Miscellaneous Antibiotics (cont’d)
linezolid (Zyvox)
New class: oxazolidinones
Used to treat vancomycin-resistant Enterococcus faecium (VREF, VRE), hospital-acquired, and skin structure infections, including those with MRSA
May cause hypotension, serotonin syndrome if taken with SSRIs, and reactions if taken with tyramine-containing foods
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20. Classroom Response Question
A patient is prescribed linezolid (Zyvox) to treat hospital-acquired pneumonia. It is most important for the nurse to determine if the patient is also taking which medication?
A diuretic
A selective serotonin reuptake inhibitor
A cardiac glycoside
A thyroid replacement drug
Correct answer: B
Rationale: Linezolid has the potential to strengthen the vasopressor (prohypertensive) effects of various vasopressive drugs such as dopamine by an unclear mechanism. Also, there have been postmarketing case reports of this drug causing serotonin syndrome when used concurrently with serotonergic drugs such as the selective serotonin reuptake inhibitor (SSRI) antidepressants. It is recommended that the SSRI be stopped while the patient is receiving linezolid therapy if possible.
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Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

21. Miscellaneous Antibiotics (cont’d)
metronidazole (Flagyl)
Used for anaerobic organisms
Intraabdominal and gynecologic infections
Protozoal infections
Several drug interactions
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22. Miscellaneous Antibiotics (cont’d)
nitrofurantoin (Macrodantin)
Primarily used for urinary tract infections (UTIs) (E. coli, Staphylococcus aureus, Klebsiella spp., Enterobacter spp.)
Use carefully if renal function is impaired
Drug concentrates in the urine
May cause fatal hepatotoxicity
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23. Miscellaneous Antibiotics (cont’d)
quinupristin/dalfopristin (Synercid)
30:70 combination, work synergistically
Used for bacteremia and infections caused by vancomycin-resistant Enterococcus (VRE) and for treatment of complicated skin and skin structure infections caused by S. pyogenes and S. aureus, including MRSA
May cause arthralgias, myalgias
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24. Miscellaneous Antibiotics (cont’d)
vancomycin (Vancocin)
Treatment of choice for MRSA and other gram-positive infections
Oral vancomycin is indicated for the treatment of antibiotic-induced colitis (C. difficile) and for the treatment of staphylococcal enterocolitis
Must monitor blood levels to ensure therapeutic levels and prevent toxicity
May cause ototoxicity and nephrotoxicity
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25. Classroom Response Question
A 58-year-old man is receiving vancomycin as part of the treatment for a severe bone infection. After the infusion, he begins to experience some itching and flushing of the neck, face, and upper body. He reports no chills or difficulty breathing. The nurse should suspect:
an allergic reaction has occurred.
an anaphylactic reaction is about to occur.
the medication will not be effective for the bone infection.
the IV dose may have infused too quickly.
Correct answer: D
Rationale: These symptoms are know as red man syndrome and may occur during or after an infusion of vancomycin. This syndrome is characterized by flushing and/or itching of the head, face, neck, and upper trunk area. Symptoms can usually be alleviated by slowing the rate of infusion to at least 1 hour. Red man syndrome is bothersome but usually not harmful. Rapid infusions may also cause hypotension.
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Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

26. Miscellaneous Antibiotics (cont’d)
vancomycin (Vancocin) (cont’d)
Red man syndrome may occur
Flushing/itching of head, neck, face, upper trunk
Antihistamine may be ordered to reduce these effects
Additive neuromuscular blocking effects in patients receiving neuromuscular blockers
Should be infused over 60 minutes
Rapid infusions may cause hypotension
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27. Miscellaneous Antibiotics (cont’d)
daptomycin (Cubicin)
Only drug of the new class known as lipopeptides
Mechanism of action is not completely known
Binds to gram-positive cells in a calcium-dependent process and disrupts the cell membrane potential
Used to treat complicated skin and soft-tissue infections caused by susceptible gram-positive bacteria, including MRSA and VRE
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28. Miscellaneous Antibiotics (cont’d)
colistimethate (Coly-Mycin)
Polypeptide antibiotic that penetrates and disrupts the bacterial membrane of susceptible strains of gram-negative bacterial
Commonly referred to as colistin
Serious adverse effects
Can cause acute respiratory failure when administered by inhalation
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29. Miscellaneous Antibiotics (cont’d)
telavancin (Vibativ)
Lipoglycopeptide
Indicated for the treatment of skin and skin structure infections caused by susceptible gram-positive organisms
Effective against MRSA and VRE
Most common adverse effects include renal toxicity, infusion-related reactions, and QT prolongation
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30. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Nursing Implications
Before beginning therapy, assess drug allergies; hepatic, renal, and cardiac function; and other lab studies
Be sure to obtain thorough patient health history, including immune status
Assess for conditions that may be contraindications to antibiotic use or that may indicate cautious use
Assess for potential drug interactions
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31. Nursing Implications (cont’d)
It is ESSENTIAL to obtain cultures from appropriate sites BEFORE beginning antibiotic therapy
Instruct patients to take antibiotics exactly as prescribed and for the length of time prescribed; they should not stop taking the medication early even if they feel better
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32. Nursing Implications (cont’d)
Assess for signs and symptoms of superinfection: fever, perineal itching, cough, lethargy, or any unusual discharge
For safety reasons, check the name of the medication carefully because there are many drugs that sound alike or have similar spellings
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33. Nursing Implications (cont’d)
Each class of antibiotics has specific adverse effects and drug interactions that must be carefully assessed and monitored
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34. Classroom Response Question
A group of office workers is concerned because a package was opened that contained a white powder substance. There is a concern that the white powder is anthrax. Which drug does the nurse anticipate being prescribed for the office workers?
daptomycin (Cubicin)
colistimethate (Coly-Mycin)
ciprofloxacin (Cipro)
quinupristin/dalfopristin (Synercid)
Correct answer: C
Rationale: Ciprofloxacin (Cipro) is the drug of choice for the treatment of anthrax (infection with Bacillus anthracis).
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35. Nursing Implications (cont’d)
Monitor for therapeutic effects
Improvement of signs and symptoms of infection
Return to normal vital signs
Negative culture and sensitivity tests
Disappearance of fever, lethargy, drainage, and redness
Monitor for adverse reactions
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