Antibiotics &
Anti-Infectives
NURS 3314: Pharmacology
Meredith French BSN, RN
Objectives
•
Recognize antimicrobials of choice for treating common infections.
•
Apply information about antimicrobials to patient care.
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Explore major concepts related to antibiotic-resistant infections, including culture and sensitivity results, and
how to act on them.
•
Predict and manage drug interactions
•
Identify patient allergies/sensitivities and intervene when necessary.
•
Evaluate the effectiveness of drug treatment for a patient, document the patient’s results, and act on the
assessment findings.
•
Manage patients experiencing side effects and adverse reactions to medications.
•
Prioritize medications to be given to a patient or a group of patients.
•
Titrate dosage of medication based on assessment and ordered parameters.
•
Verify the appropriateness and accuracy of an order for medication.
Basic Principles of
Antimicrobial Therapy
• Most widely used groups of medicines (190 million
doses are given in hospitals each day)
• Used to treat infectious diseases
• Debut in 1930s and 1940s, and have greatly reduced
morbidity and mortality from infection
Basic Principles
• Antibiotic
• chemical that is produced by one microbe and has the
ability to harm other microbes
• Antimicrobial drug
• Any agent, natural or synthetic, that has the ability to
kill or suppress microorganisms
Selective Toxicity
• “Ability of a drug to injure a target cell or organisms
without injuring other cells or organisms that are in
intimate contact with the target.”
• Highly toxic to microbes, but harmless to host
• Difference in the cellular chemistry of mammals and
microbes
• Disruption of the bacterial cell wall
• Inhibition of an enzyme unique to bacteria
Classification of
Antimicrobial Drugs
• Cell wall synthesis:
• Cell membrane permeability:
• Protein synthesis:
• Nonlethal inhibitors of protein synthesis:
• Synthesis of nucleic acids:
• Antimetabolites:
• Viral enzyme inhibitors:
Classification of Antibiotics
• Bacteriocidal
• Drugs are directly lethal to bacteria at clinically
achievable concentrations
• Bacteriostatic
• Drugs can slow bacterial growth but do not cause cell
death
Acquired Resistance to Antimicrobial Drugs
• Over time, organisms develop resistance
• 4 basic actions
• Decrease the concentration of a drug at its site of
action
• Inactivate a drug
• Alter the structure of drug target molecules
• Produce a drug antagonist
Antibiotic Use and DrugResistant Microbe Emergence
• How antibiotic use promotes resistance
• Antibiotics that promote resistance
• The extent of antibiotic use affects resistance
• Nosocomial infections
• Superinfection
• New infection that appears during the course of
treatment for a primary infection
Delaying Emergence of
Drug Resistance
• Promote adherence to appropriate prescribing
guidelines
• Reduce demand for antibiotics among healthy adults
and parents of young children
• Emphasize adherence to prescribed antibotic
regimens
Selection of Antibiotics
• Identify organism (match drug with bug, gram-stained
preparation, determining drug susceptibility)
• Drug sensitivity of organism
• Host factors (host defenses, site of infection, previous
allergic reactions, genetic factors)
• Drug may be ruled out owing to:
• Allergy
• Inability to penetrate site of infection
• Patient variables
Antibiotic Combinations
• Antimicrobial effects of antibiotic combinations
• Indications
• Advantages: reduced toxicity, reduced resistance,
reduced risk in severe infection
• Disadvantages of combinations
Prophylactic Use
• Agents are given to prevent infection:
•
•
•
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Surgery
Bacterial endocarditis
Neutropenia
Other indications
What to teach patients…
• Do not discontinue prematurely… Complete full
prescription!
• Stop and notify physician of any signs of allergic
reactions
• Notify physician of any side effects
• Do not share with anyone else
• Keep in a cool, dry place away from the reach of
children
Question
A patient is prescribed an antibiotic to treat a urinary tract
infection. What statement by the patient indicates a need for
further teaching?
A. “I can stop the medication as soon as the symptoms
disappear.”
B. “I will drink more fluids to help clear up the infection.”
C. “I will stop the medication and contact the doctor if I
develop a rash.
D. “I should immediately report vaginal itching or
discharge.”
Question
Which patient should receive prophylactic antibiotic
therapy?
A. A patient who is to have his teeth cleaned
B. A patient who is scheduled for a hysterectomy
C. A patient with a white blood cell count of 8000
cells/mm3
D. A patient with a high fever without an identifiable
cause
Penicillins
• MOA: weaken the cell wall, causing bacteria to take
up excessive water and rupture; bacteriocidal
• Active against a variety of bacteria
• Principal adverse effect: allergic reaction
• Bacterial resistance
• Inability of penicillins to reach their target
• Inactivation of penicillins by bacterial enzymes
• Methicillin-resistant Staphylococcus aureus (MRSA)
Cell Envelope
• Gram-negative cell envelope
• Three layers
• Thin cell wall and an additional outer membrane that is
difficult to penetrate
• Gram-positive cell envelope
• Only two layers
• Relatively thick cell wall that is easily penetrated
Penicillin G
(Benzylpenicillin)
• Bactericidal to numerous gram-positive and some
gram-negative organisms
• Adverse effects
• Least toxic of all antibiotics
• Penicillins are the most common cause of drug allergy
Penicillin G cont’d…
• DOC:
Clinical indication
Infecting organism
Pneumonia
Streptococcus pneumoniae
Pharyngitis
Streptococcus pyogenes
Endocarditis
Streptococcus viridans
Gas gangrene
Clostridium perfringens
Tetanus
Clostridium tetani
Anthrax
Bacillus anthracis
Meningitis
N. Meningitidis
Syphilis
Spirochete T. pallidum
Amoxicillin
• Broad-spectrum penicillin
• Same antimicrobial spectrum as penicillin G, plus
increased activity against certain gram-negative
bacilli (H. influenzae, E. coli, Salmonella, & Shigella)
• Reduce dose for renal impairment
• s/e: rash and diarrhea
Nafcillin
• Penicillinase-resistant penicillin
Amoxicillin/clavulanate (Augmentin) &
Piperacillin/tazobactam (Zosyn)
• Extends antimicrobial spectrum when combined
with penicillinase-sensitive antibiotics
Penicillin Allergy
• Between 0.4% and 7% of patients who receive
penicillins experience an allergic reaction.
• Classified
• Immediate: 2 to 30 minutes after
• Accelerated: 1 to 72 hours
• Delayed: days to weeks
• Minor rash to anaphylaxis (laryngeal edema,
bronchoconstriction, severe hypotension)
Question
A patient with a history of a severe anaphylactic reaction to
penicillin has an order to receive cephalosporin. What
should the nurse do?
A. Administer the cephalosporin as ordered.
B. Contact the healthcare provider for a different antibiotic.
C. Administer a test dose of cephalosporin to determine
reactivity.
D. Have an epinephrine dose available when administering
the cephalosporin.
Question
A patient with an infection caused by Pseudomonas aeruginosa
is being treated with piperacillin. The nurse providing care
reviews the patient’s laboratory results and notes that the
patient’s BUN and serum creatinine levels are elevated. The
nurse will contact the provider to discuss:
A. adding an aminoglycoside.
B. changing to penicillin G.
C. reducing the dose of piperacillin.
D. ordering nafcillin.
Cephalosporins
• Most widely used group of antibiotics
• Beta-lactam antibiotics
• Bactericidal
• Similar to penicillin in structure and action
• MOA: bind to penicillin-binding proteins (PBPs),
disrupt cell wall synthesis, and cause cell lysis
• Most effective against cells undergoing active growth
and division
• Resistance
Classification of Cephalosporins
•
First generation (prophylaxis against infection in surgical patients; rarely
used for active infections)
• Cephalexin
•
Second generation (rarely used for active infection)
• Cefoxitin
•
Third generation (highly active against gram-negative infections, able to
penetrate CSF)
• Cefotaxime
•
Fourth generation (commonly used to treat hospital-associated
pneumonias, including those caused by resistant organism Pseudomonas)
• Cefepime
•
Fifth generation (infections associated with MRSA)
• Ceftaroline
Carbapenems
• Imipenem (Primaxin)
• Active against most bacterial pathogens
• Highly active against gram-positive cocci and most
gram-negative cocci and bacilli
• Most effective beta-lactam antibiotic for use against
anaerobic bacteria
Vancomycin
• MOA: inhibits cell wall synthesis
• Uses: severe infections only, MRSA, Staphylococcus
epidermidis, Clostridium difficile
• a/e: ototoxicity, “red man” syndrome,
thrombophlebitis, thrombocytopenia, allergy
Question
A patient is to undergo orthopedic surgery, and the
prescriber will order a cephalosporin to be given
preoperatively. The nurse expects the provider to order
which cephalosporin?
A. first generation
B. second generation
C. third generation
D. fourth generation
Question
A patient is prescribed vancomycin for antibioticassociated pseudomembranous colitis. The nurse will
monitor for what?
A. Leukopenia
B. “Red man” syndrome
C. Liver impairment
D. Ototoxicity
Tetracyclines
• Broad-spectrum antibiotics
• Inhibit protein synthesis
• Increasing bacterial resistance has emerged
Tetracycline uses:
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•
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Tx of infectious disease
Tx of acne
Peptic ulcer disease
Periodontal disease
Rheumatoid arthritis
Mycoplasma pneumoniae
Lyme disease
Anthrax
Helicobacter pylori
Tetracyclines
• Absorption
• Drug & food interaction:
• Calcium supplements, milk products, iron supplements,
magnesium-containing laxatives, and most antacids
• a/e:
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•
•
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GI irritation
Effects on bone and teeth
Superinfection
Hepatoxicity
Renal toxicity
Photosensitivity and other effects
Macrolides (erythromycin)
• Broad-spectrum antibiotic
• MOA: inhibition of protein synthesis
• Usually bacteriostatic, but can be bactericidal
• Used if patient allergic to penicillin
• Active against most gram-positive and some gramnegative bacteria
Erythromycin cont’d…
• Uses:
• Whooping cough, acute diptheria, Corynebacterium
diptheria, chlamydial infections, M. pneumoniae, group A
Streptococcus pyogenes
• May be used as alternative to penicillin G in patients
with penicillin allergy
• Drug interactions
• a/e: GI, QT prolongation and sudden cardiac death,
superinfections, thrombophlebitis, transient hearing
loss
Clindamycin (Cleocin)
• Can promote severe Clostridium difficile – associated
diarrhea
• Active against most anaerobic bacteria (grampositive and gram-negative)
• Indicated only for certain anaerobic infections
outside the CNS
• Alternative to penicillin
Clindamycin (Cleocin)
• a/e:
•
•
•
•
•
CDAD
Hepatic toxicity
Blood dyscrasias
Diarrhea
Hypersensitivity reactions
Linezolid (Zyvox)
• Bacteriostatic inhibitor of protein synthesis
• Active against multidrug-resistant, gram-positive
pathogens (VRE and MRSA)
• s/e: diarrhea, n/v, headache, myelosuppresion
• Drug interaction: monoamine oxidase inhibitors
(MAOIs)
Question
A patient is prescribed doxycycline (Vibramycin). If the
patient complains of gastric irritation, what should the nurse
do?
A. Instruct the patient to take the medication with milk
B. Tell the patient to take an antacid with the medication
C. Give the patient food, such as crackers or toast, with the
medication
D. Have the patient stop the medication immediately and
contact the healthcare provider
Question
A pregnant adolescent patient asks the nurse whether she should
continue to take her prescription for tetracycline (Sumycin) to clear
up her acne. Which response by the nurse is correct?
A. “Tetracycline can be harmful to the baby’s teeth and should be
avoided.”
B. “Tetracycline is safe to take during pregnancy.”
C. “Tetracycline may cause allergic reactions in pregnant
woman.”
D. “Tetracycline will prevent asymptomatic urinary tract
infections.”
Question
A 6-week-old infant who has not yet received
immunizations develops a severe cough. While
awaiting nasopharyngeal culture results, the nurse will
expect to administer which antibiotic?
A. Clindamycin (Cleocin)
B. Doxycycline (Vibramycin)
C. Erythromycin ethylsuccinate
D. Penicillin G
Aminoglycosides
• Narrow-spectrum antibiotics
• Bactericidal
• Use: aerobic gram-negative bacilli
• Can cause serious injury to inner ear and kidney
• Microbial resistance
Aminoglycosides
• a/e:
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•
•
•
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Nephrotoxicity
Ototoxicity
Hypersensivity reactions
Neuromuscular blockade
Blood dyscrasias
• DOC: reversal with IV infusion of a calcium salt (ex.
Calcium gluconate)
• Drug interactions
Serum levels
• The same aminoglycoside dose can produce a very
different plasma level in different patients
• Peak levels must be high enough to kill bacteria;
trough levels must be low enough to minimize
toxicity
• Samples for…
• peak levels: 30 minutes after IM injection or IV infusion
• Trough levels: depends on dosing schedule
Gentamicin
• Used to treat serious infections caused by aerobic
gram-negative bacilli
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•
•
•
•
Pseudomonas aeruginosa
Escherichia coli
Klebsiella
Serratia
Proteus mirabilis
• a/e: nephrotoxicity and ototoxicity
Amikacin (Amikin)
• Of all the aminoglycosides, amikacin is active
against the broadest spectrum of gram-negative
bacilli and is the least vulnerable to inactivation by
bacterial enzymes
• DOC: when gentamicin is resistant in hospitals
• Toxic to the kidneys and inner ears
Question
The nurse is reviewing lab values from a patient who has
been prescribed gentamicin. To prevent ototoxicity, it is most
important for the nurse to monitor which value(s)?
A. Serum creatinine and BUN levels
B. Trough drug levels of gentamicin
C. Peak drug levels of gentamicin
D. Serum alanine aminotransferase and asparate
aminotransferase levels
Question
The patient is ordered daily divided doses of
gentamicin. The patient received an intravenous dose
of gentamicin at 1600. When should the nurse obtain
the peak level?
A. 1630
B. 1700
C. 1730
D. 1800
Question
A patient is receiving an intraperitoneal
aminoglycoside during surgery. To reverse a serious
side effect of this drug, the nurse may expect to
administer which agent?
A. Amphotericin B
B. Calcium gluconate
C. Neuromuscular blocker
D. Vancomycin
Sulfonamides
• Broad-spectrum antibiotics
• Suppress bacterial growth by inhibiting
tetrahydrofolic acid, a derivative of folic acid or
folate
• DOC: UTI
• Other uses: nocardiosis, Chlamydia trachomatis,
conjugation therapy for toxoplasmosis/malaria,
ulcerative colitis
Sulfonamides cont’d…
• a/e: hypersensitivity reactions (Stevens-Johnson
syndrome), hematologic effects, kernicterus, renal
damage from crystalluria
• Drug interactions
• Microbial resistance
• Many bacterial species have developed resistance to
sulfonamides (especially among gonococci, meningococci,
streptococci, and shigella)
• May be acquired by spontaneous mutation or by transfer of
plasmids that code for antibiotic resistance (R factors)
Silver Sulfadiazine
(Silvadene)
• Use: to suppress bacterial colonization in patients
with 2nd and 3rd degree burns
• Application is usually pain free
• Systemic absorption
• Mafenide: acidosis
Trimethoprim/sulfamethoxazole
(Bactrim)
• Inhibits sequential steps in bacterial folic acid
synthesis, making it much more powerful than TMP
or SMZ alone
• Plasma drug levels
• Uses:
• UTI, otitis media, bronchitis, shigellosis, pneumonia
caused by Pneumocystis jiroveci, Pnemocystis pneumonia,
and GI infection
Trimethoprim/sulfamethoxazole
(Bactrim) cont’d…
• a/e:
•
•
•
•
GI (n/v)
Rash
Hyperkalemia
Hypersensitivity reactions (Stevens-Johnson syndrome)
• Blood dyscrasias
• Kernicterus
• Renal damage: crystalluria
Question
A patient will be discharged from the hospital with
prescription for TMP/SMZ (Bactrim). When providing
teaching for this patient, the nurse will tell the patient
that it will be important to:
A. drink 8 to 10 glasses of water each day,
B. eat foods that are high in potassium.
C. take the medication with food.
D. take folic acid supplements.
Question
A patient with bronchitis is taking TMP/SMZ, 160/800mg
orally, twice daily. Before administering the third dose, the nurse
notes that the patient has a widespread rash, a temperature of
103F, and a heart rate of 100 beats per minute. The patient looks
ill and reports not feeling well. What will the nurse do?
A. Administer the dose and request an order for an antipyretic
medication.
B. Withhold the dose and request an order for an antihistamine
to treat the rash.
C. Withhold the dose and notify the provider of the symptoms.
D. Request and order for intravenous TMP/SMZ, because the
patient is getting worse.
Drug Therapy of UTIs
• TMP/SMZ (Bactrim) and nitrofurantoin
Acute Cystitis
• Lower UTI that occurs most in women of child-bearing
age
• s/s: dysuria, urinary urgency and frequency, suprapubic
discomfort, pyuria, and bacteriuria
• DOC
• Uncomplicated: TMP/SMZ (Bactrim) or nitrofurantoin
• Communities where resistance exceeds 20%:
fluoroquinolones (ciprofloxacin, norfloxacin)
• Adherence is a concern: single-dose fosfomycin
Acute Uncomplicated
Pyelonephritis
• Infection of the kidneys
• Common in young children, older adults, women of
child-bearing age
• s/s: fever, chills, severe flank pain, dysuria, urinary
frequency & urgency, pyuria, and usually bacteriuria
• Mild to moderate infection: TMP/SMZ (Bactrim),
trimethoprim alone, ciprofloxacin, and levofloxacin
• Severe infection: hospitalization and IV antibiotics
Acute Bacterial Prostatis
• Inflammation of the prostate caused by local bacterial
infection
• s/s: high fever, chills, malaise, myalgia, localized pain,
and various urinary tract symptoms
• Responds well to antimicrobial therapy. Drug selection
and route depend of organism and severity.
• E. coli: IV agent (fluoroquinolone such as ciprofloxacin
followed by oral agent (doxycycline or fluoroquinolone)
• Vancomycin-sensitive E. faecalis: IV ampicillin/sulbactam
then PO amoxicillin, levofloxacin, or doxycycline
Nitrofurantoin (Macrodantin)
• Urinary tract antiseptics
• Low concentrations: Bacteriostatic
• High concentrations: Bactericidal
• Uses: lower UTIs (bladder and urethra), prophylaxis,
recurrent lower UTIs
Nitrofurantoin (Macrodantin)
cont’d…
• a/e:
•
•
•
•
•
•
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GI effects
Pulmonary reactions
Hematologic effects
Peripheral neuropathy
Hepatotoxicity
Birth defects
Other
Question
A patient with a history of renal calculi has fever, flank pain, and
bacteriuria. The nurse caring for this patient understands that it is
important for the provider to:
A. begin antibiotic therapy after urine culture and sensitivity
results are available.
B. give prophylactic antibiotics for 6 weeks after the acute
infection has cleared.
C. initiate immediate treatment with broad-spectrum antibiotics.
D. refer the patient for intravenous antibiotics and
hospitalization.
Fluoroquinolones
• Broad-spectrum agents with multiple applications
• Disrupt DNA replication and cell division
• s/e: generally mild but can cause tendon rupture
(low risk)
• Usually affects Achilles tendon
• Avoid in patients younger than 18 years
• Risk to those older than 60 years those take
glucocorticoids, and those who have undergone kidney,
heart, or lunch transplant
Ciprofloxacin (Cipro)
• Gram-negative and some gram-positive organisms
• Inhibits bacterial DNA gyrase and topoisomerase II
• DOC: anthrax
• Infection uses: respiratory, UTIs, GI, bones, joints,
skin, and soft tissue
• Bacterial resistance: S. aureus, Serratia marcescens,
Campylobacter jejuni, Pseudomonas aeruginosa, &
Neisseria gonorrhoeae
Ciprofloxacin cont’d…
• a/e
• Mild
• GI: n/v, diarrhea, abdominal pain
• CNS: dizziness, headache, restlessness, confusion, rarely
seizures
• Tendon rupture
• Phototoxicity
• Candida infections: Pharynx and vagina
• Increased risk for C. diff infection
• Older adult patients
• Confusion, somnolence, psychosis, visual disturbances
• Myasthenia gravis
Ciprofloxacin cont’d…
• Drug and food interactions
• Cationic compounds
• Absorption reduced by:
• Aluminum antacids, magnesium antacids, iron salts, zinc
salts, sucralfate, milk and diary products
• Elevation of drug levels
• Theophylline (used for asthma)
• Warfarin (an anticoagulant)
• Tinidazole (an antifungal drug)
Metronidazole (Flagyl)
• Bactericidal
• Uses:
•
•
•
•
Protozoal infections
Infections caused by obligate anaerobes
Helicobacter pylori
C. diff
• a/e:
• Neurotoxicity
• Allergy
• superinfections
Question
It is important for the nurse to avoid administering oral
ciprofloxacin to this patient with which food?
A. Bananas
B. Baked chicken
C. Grapefruit juice
D. Milk
Question
A patient is diagnosed with C. difficile infection. The
nurse anticipates administering which medication?
A. Daptomycin
B. Metronidazole
C. Rifampin
D. Rifaximin
Amphotericin B
(Abelcet)
• Broad-spectrum antifungal
• Binds to components of the fungal cell membrane,
increasing permeability
• DOC for most systemic mycoses
• Highly toxic; therefore, should only be employed against
infections that are progressive and potentially fatal
• a/e: infusion reactions, nephrotoxicity, hypokalemia,
hematologic effects
Azoles
• Broad-spectrum antifungal drugs
• Lower toxicity and can be given by mouth
Itraconazole (Sporanox)
• Inhibits the synthesis of ergosterol; the result is
increased permeability and leakage of cellular
components
• Safer than amphotericin B and can be taken orally
• DOC: blastomycosis, histoplasmosis,
paracoccidioidomycosis, and sporotrichosis
• a/e: GI (n/v, diarrhea), rash, headache, abdominal
pain, edema
• Serious a/e: cardiosuppression and liver injury
Ketoconazole (Nizoral)
• Active against most fungi that cause systemic mycoses, as
well as fungi that cause superficial infections
(dermatophytes and Candida species)
• a/e:
• n/v (give drug with food), hepatoxicity, effects on sex
hormones, rash, itching, dizziness, fever, chills, constipation,
diarrhea, photophobia, and headache
• Fatal hepatic necrosis
• Inhibits CYP3A4 and can increase levels of other drugs
Fluconazole (Diflucan)
• MOA: same as itraconazole
• Uses: blastomycosis, histoplasmosis, meningitis caused by
cryptococcus neoformans and Coccidioides immitis; and
vaginal, oropharyngeal, esophageal, and disseminated Candida
infections.
• Can cause serious birth defects if taken in 1st trimester
• Can inhibit CYP3A4 and increase levels of other drugs
(warfarin, phenytoin, cyclosporine, zidovudine, rifabutin,
and sulfonylurea oral hypoglycemics)
Clotrimazole
• DOC: dermatophytic infections and candidiasis of the
skin, mouth, and vagina
• a/e
• Topical administration: stinging, erythema, edema, urticaria,
pruritus, and peeling; however, the incidence is low
• Intravaginal administration: burning sensation and lower
abdominal cramps
• Oral: GI distress
• Try this topical cream before using ketoconazole PO
because of the toxicity associated with oral use
Nystatin
• Polyene antibiotic used only for candidiasis
• DOC: intestinal candidiasis, but can also treat
candidal infections of the skin, mouth, esophagus,
and vagina
• a/e
• Oral: GI disturbance (n/v, diarrhea)
• Topical: local irritation
Question
A patient who is receiving intravenous ciprofloxacin for
pneumonia develops diarrhea. A stool culture is
positive for Clostridium difficule. The nurse will expect
the provider to:
A. add metronidazole (Flagyl)
B. increase the dose of ciprofloxacin
C. restrict diary products
D. switch to gemifloxacin
Question
A nursing student asks a nurse to explain the differences
between amphotericin B (Abelcet) and the azoles group of
antifungal agents. Which statement by the nurse is correct?
A. “Amphotericin B can be given orally or intravenously.”
B. “Amphotericin B increases the levels of many other
drugs.”
C. “Azoles have lower toxicity than Amphotericin B.”
D. “Only the azoles are broad-spectrum antifungal agents.”