1. CHAPTER 39 Antibiotics Part 2

2. Antibiotic Therapy: Concepts
Multidrug resistance
Therapeutic drug monitoring
Minimum inhibitory concentration (MIC)
Time-dependent killing
Concentration-dependent killing
Once-daily dosing vs. multi-daily dosing
Peak and trough blood levels
Synergistic effects
Post-antibiotic effect (PAE)

3. Antibiotic Therapy: Toxicities
Ototoxicity
Temporary or permanent hearing loss, balance problems
Nephrotoxicity
Varying degrees of reduced renal function
Rising serum creatinine may indicate reduced creatinine clearance
Monitor trough levels every 5 to 7 days while on therapy or as ordered
Monitor serum creatinine levels at least every 3 days as an index of renal function

4. Aminoglycosides gentamicin (Garamycin) neomycin (Neo-fradin)
tobramycin (Nebcin)
amikacin (Amikin)
kanamycin
streptomycin

5. Aminoglycosides (cont’d)
Natural and semisynthetic
Produced from Streptomyces
Poor oral absorption; no PO forms
Very potent antibiotics with serious toxicities
Bactericidal; prevent protein synthesis
Kill mostly gram-negative bacteria; some gram-positive also

6. Aminoglycosides: Indications
Used to kill gram-negative bacteria such as
Pseudomonas spp., E. 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

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

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

9. Aminoglycosides: Adverse Effects (cont’d)
Ototoxicity and nephrotoxicity are
the most significant
Headache
Paresthesia
Fever
Superinfections
Vertigo
Skin rash
Dizziness

10. Quinolones ciprofloxacin (Cipro) norfloxacin (Noroxin)
levofloxacin (Levaquin)
moxifloxacin (Avelox)

11. Quinolones (cont’d) Also called “fluoroquinolones”
Excellent oral absorption
Absorption reduced by antacids
Effective against gram-negative organisms and some gram-positive organisms

12. Quinolones: Mechanism of Action
Bactericidal
Alter DNA of bacteria, causing death
Do not affect human DNA

13. Quinolones: Indications
Gram-negative bacteria such as pseudomonas
Respiratory infections
Bone and joint infections
GI infections
Skin infections
Sexually transmitted diseases
Anthrax

14. Fluoroquinolones: Adverse Effects
Body System Adverse Effects
CNS Headache, dizziness, fatigue, depression, restlessness, insomnia
GI Nausea, vomiting, diarrhea, constipation, thrush, increased liver function studies, others
Cardiac Prolonged QT interval

15. Fluoroquinolones: Adverse Effects (cont’d)
Body System Adverse Effects
Integumentary Rash, pruritus, urticaria, flushing, photosensitivity (with lomefloxacin)
Other Fever, chills, blurred vision, tinnitus
Black box warning: increased risk of tendonitis and tendon rupture

16. Other Antibiotics clindamycin (Cleocin) linezolid (Zyvox)
metronidazole (Flagyl)
nitrofurantoin (Macrodantin)
quinupristin and Dalfopristin (Synercid)
daptomycin (Cubicin)
vancomycin (Vancocin)
colistimethate (Coly-mycin)

17. Other Antibiotics (cont’d)
clindamycin (Cleocin)
Used for chronic bone infections, GU infections, intraabdominal infections, other serious infections
May cause pseudomembranous colitis

18. Other Antibiotics (cont’d)
linezolid (Zyvox)
New class: oxazolidinones
Used to treat vancomycin-resistant Enterococcus faecium (VREF, VRE), hospital-acquired skin 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

19. Other Antibiotics (cont’d)
metronidazole (Flagyl)
Used for anaerobic organisms
Intraabdominal and gynecologic infections
Protozoal infections
Several drug interactions

20. Other Antibiotics (cont’d)
nitrofurantoin (Macrodantin)
Primarily used for UTIs (E. coli, S. aureus, Klebsiella spp., Enterobacter spp.)
Use carefully if renal function is impaired
Drug concentrates in the urine
May cause fatal hepatotoxicity
Usually well-tolerated if patient is kept well-hydrated

21. Other Antibiotics (cont’d)
quinupristin and dalfopristin (Synercid)
30:70 combination, work synergistically
Used for bacteremia and infections caused by vancomycin-resistant Enterococcus (VRE) and other complicated skin infections
May cause arthralgias, myalgias

22. Other Antibiotics (cont’d)
daptomycin (Cubicin)
New class: lipopeptide
Used to treat complicated skin and
soft-tissue infections

23. Other Antibiotics (cont’d)
vancomycin (Vancocin)
Natural, bactericidal antibiotic
Destroys cell wall
Treatment of choice for MRSA and other
gram-positive infections
Must monitor blood levels to ensure therapeutic levels and prevent toxicity
May cause ototoxicity and nephrotoxicity
Should be infused over 60 minutes
Rapid infusions may cause hypotension

24. Other Antibiotics (cont’d)
vancomycin (Vancocin) (cont’d)
Monitor IV site closely
Red man syndrome may occur
Flushing/itching of head, neck, face, upper trunk
Antihistamine may be ordered to reduce these effects
Ensure adequate hydration (2 L fluids/24 hr) if not contraindicated to prevent nephrotoxicity
Monitor trough levels carefully

25. 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

26. 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 when they feel better

27. 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

28. Nursing Implications (cont’d)
Each class of antibiotics has specific adverse effects and drug interactions that must be carefully assessed and monitored

29. Nursing Implications (cont’d)
Aminoglycosides
Monitor peak and trough blood levels of these drugs to prevent nephrotoxicity and ototoxicity
Symptoms of ototoxicity include dizziness, tinnitus, and hearing loss
Symptoms of nephrotoxicity include urinary casts, proteinuria, and increased BUN and serum creatinine levels

30. 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