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CHAPTER 39

Antibiotics Part 2

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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)

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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

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Aminoglycosides

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

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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

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Aminoglycosides: Indications

Used to kill gram-negative bacteria such asPseudomonas 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

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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

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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

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Aminoglycosides: Adverse Effects (cont’d)

Ototoxicity and nephrotoxicity are the most significant Headache Paresthesia Fever Superinfections

Vertigo Skin rash Dizziness

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Quinolones

ciprofloxacin (Cipro) norfloxacin (Noroxin) levofloxacin (Levaquin) moxifloxacin (Avelox)

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Quinolones (cont’d)

Also called “fluoroquinolones” Excellent oral absorption Absorption reduced by antacids Effective against gram-negative organisms

and some gram-positive organisms

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Quinolones: Mechanism of Action

Bactericidal Alter DNA of bacteria, causing death Do not affect human DNA

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Quinolones: Indications

Gram-negative bacteria such as pseudomonas

Respiratory infections Bone and joint infections GI infections Skin infections Sexually transmitted diseases Anthrax

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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

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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

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Other Antibiotics

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

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Other Antibiotics (cont’d)

clindamycin (Cleocin) Used for chronic bone infections, GU infections,

intraabdominal infections, other serious infections May cause pseudomembranous colitis

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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

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Other Antibiotics (cont’d)

metronidazole (Flagyl) Used for anaerobic organisms Intraabdominal and gynecologic infections Protozoal infections Several drug interactions

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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

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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

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Other Antibiotics (cont’d)

daptomycin (Cubicin) New class: lipopeptide Used to treat complicated skin and

soft-tissue infections

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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

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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

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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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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

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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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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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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

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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