6/3/24, 9:45 PM Exam 2 NSG 124 Study Guide
NSG124 Pharmacology Study Test Plan EXAM 2
Unit 2 Module 5 & 6 Location Student Notes
Antimicrobial NSG124.05.01.01 *Antibiotic is a chemical that is produced by one microbe and has the ability
Identify subcategories: Antimicrobial Basics to harm other microbes. Under this definition, only those compounds that
Selective toxicity is defined as the ability of a drug to injure a target Antibiotic and antimicrobial drug: the formal are actually made by microorganisms qualify as antibiotics.
cell or target organism without injuring other cells or organisms that definitions of these words are not identical *An antimicrobial drug is defined as any agent, natural or synthetic, that has
are in intimate contact with the target. the ability to kill or suppress microorganisms. Under this definition, no
Some agents, called narrow-spectrum antibiotics, are active against distinction is made between compounds produced by microbes and those
only a few species of microorganisms. In contrast, broad-spectrum made by chemists.
antibiotics are active against a wide variety of microbes.
Dosage and duration of treatment: Success requires that the NSG124.05.01.02 Mixed Infections
antibiotic be present at the site of infection in an effective Antibiotic Dosing, Duration, & Rational for An infection may be caused by more than one microbe. Multiple infectious
concentration for a sufficient time. Dosages should be adjusted to Combination Therapy: The most common organisms are common in brain abscesses, pelvic infections, and infections
produce drug concentrations that are equal to or greater than the indication for using multiple antibiotics is initial resulting from perforation of abdominal organs.
MIC for the infection being treated. Drug levels 4 to 8 times the MIC therapy of a severe infection of unknown Preventing Resistance
are often desirable. etiology, especially in the neutropenic host. Although the use of multiple antibiotics is usually associated
Therapy with antibiotic combinations: When two antibiotics are Until the infecting organism has been with promoting drug resistance, there is one infectious disease—tuberculosis
used together, the result may be additive, potentiative, or, in certain identified, wide antimicrobial coverage is —in which drug combinations are employed for the specific purpose
cases, antagonistic. An additive response is one in which the appropriate. Just how broad the coverage of suppressing the emergence of resistant bacteria.
antimicrobial effect of the combination is equal to the sum of the should be depends on the clinician's skill in Decreased Toxicity
effects of the two drugs alone. A potentiative interaction (also called narrowing the field of potential pathogens. In some situations, an antibiotic combination can reduce toxicity to the host.
a synergistic interaction) is one in which the effect of the Once the identity of the infecting microbe is For example, by combining flucytosine with amphotericin B in the treatment
combination is greater than the sum of the effects of the individual known, drug selection can be adjusted of fungal meningitis, the dosage of amphotericin B can be reduced, thereby
agents. In certain cases, a combination of two antibiotics may accordingly. decreasing the risk of amphotericin-induced damage to the kidneys.
be less effective than one of the agents by itself, Disadvantages of Antibiotic Combinations Enhanced Antibacterial Action
inducing antagonism between the drugs. The use of multiple antibiotics has several In specific infections, a combination of antibiotics can have greater
drawbacks, including (1) increased risk of toxic antibacterial action than a single agent. This is true of the combined use of
and allergic reactions, (2) possible antagonism penicillin plus an aminoglycoside in the treatment of enterococcal
of antimicrobial effects, (3) increased risk of endocarditis. Penicillin acts to weaken the bacterial cell wall; the
superinfection, (4) selection of drug-resistant aminoglycoside acts to suppress protein synthesis.
bacteria, and (5) increased cost. Accordingly,
antimicrobial combinations should be
employed only when clearly indicated.
* Prophylactic use: Prophylactic use of antibiotics can decrease the NSG124.05.01.03 Monitoring antimicrobial
incidence of infection in certain kinds of surgery. Procedures in which *Improper Dosage *Antimicrobial therapy is assessed by monitoring clinical responses and
prophylactic efficacy has been documented include cardiac surgery, Like all other medications, antibiotics must be laboratory results. The frequency of monitoring is directly proportional to the
peripheral vascular surgery, orthopedic surgery, and surgery on the GI tract used in the right dosage. If the dosage is too severity of infection. Important clinical indicators of success are reduction of
(stomach, duodenum, colon, rectum, and appendix). low, the patient will be exposed to a risk of fever and resolution of signs and symptoms related to the affected organ
Misuses of antimicrobial: a) Use in the absence of appropriate surgical adverse effects without benefit of antibacterial system (e.g., improvement of breath sounds in patients with pneumonia).
drainage. b) antimicrobial therapy administered without adequate effects. If the dosage is too high, the risks of * Various laboratory tests are used to monitor treatment. Serum drug levels
bacteriologic information superinfection and adverse effects become may be monitored for two reasons: to ensure that levels are sufficient for
*Attempted Treatment of Viral Infection unnecessarily high. antimicrobial effects and to avoid toxicity from excessive levels. The success
The majority of viral infections—including mumps, chickenpox, and the *Treatment in the Absence of Adequate of the therapy is indicated by the disappearance of infectious organisms from
common cold—do not respond to currently available drugs. Bacteriologic Information post-treatment cultures.
*Treatment of Fever of Unknown Origin As stressed earlier, proper antimicrobial *Cultures may become sterile within hours of the onset of treatment (as may
Although fever can be a sign of infection, it can also signify other diseases, therapy requires information on the identity happen with urinary tract infections), or they may not become sterile for
including hepatitis, arthritis, and cancer. Unless the cause of a fever is a and drug sensitivity of the infecting organism. weeks (as may happen with tuberculosis).
proven infection, antibiotics should not be employed. *Omission of Surgical Drainage
Antibiotics may have limited efficacy in the
presence of foreign material, necrotic tissue, or
exudate. Hence, when appropriate, surgical
drainage and cleansing should be performed to
promote antimicrobial effects.
Introduction to Penicillins NSG124.05.02.01 Penicillins weaken the cell wall by two actions: **Penicillin Class: Broad-spectrum penicillins (aminopenicillins) Drug:
Broad vs Narrow: The most useful classification of penicillins is (1) inhibition of transpeptidases and Ampicillin, Amoxicillin. Clinically Useful Antimicrobial Spectrum:
based on an antimicrobial spectrum. When classified this way, the (2) disinhibition (activation) of autolysins. Haemophilus influenzae, Escherichia coli, Proteus
penicillins fall into four major groups: (1) narrow-spectrum **Penicillin Class: Narrow-spectrum penicillins: mirabilis, enterococci, Neisseria gonorrhoeae
penicillins that are penicillinase sensitive, (2) narrow-spectrum penicillinase sensitive: Drug: Penicillin G, **Penicillin Class: Extended-spectrum penicillin (antipseudomonal penicillin)
penicillins that are penicillinase resistant (antistaphylococcal Penicillin V Clinically Useful Antimicrobial Drug: Piperacillin. Clinically Useful Antimicrobial Spectrum: Same as broad-
penicillins), (3) broad-spectrum penicillins (aminopenicillins), and (4) Spectrum: treptococcus species, Neisseria spectrum penicillins plus Pseudomonas aeruginosa,
extended-spectrum penicillins (antipseudomonal penicillins). species, many anaerobes, spirochetes, others Enterobacter species, Proteus (indole positive), Bacteroides
Penicillin Action, Use, & Resistance **Penicillin Class: Narrow-spectrum penicillins: fragilis, many Klebsiella
Penicillins weaken the cell wall, causing bacteria to take up excessive penicillinase resistant (antistaphylococcal
amounts of water and rupture. As a result, penicillins are penicillins) Drug: Nafcillin, Oxacillin, Dicloxacillin
generally bactericidal. However, it is important to note that penicillins are Clinically Useful Antimicrobial Spectrum:
active only against bacteria that are undergoing growth and division. Staphylococcus aureus.
Side Effects and Toxicities: NSG124.05.02.02 x2 Penicillin Action, Effect, Toxicity, Allergy, & Penicillin reactions are classified as immediate,
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, 6/3/24, 9:45 PM Exam 2 NSG 124 Study Guide
Severe: Inadvertent intra-arterial injection can produce severe Interactions accelerated, and delayed. Immediate reactions occur 2 to 30 minutes after
reactions—gangrene, necrosis, sloughing of tissue—and must be Penicillin G is the least toxic of all antibiotics drug administration; accelerated reactions occur within 1 to 72 hours;
avoided. and among the safest of all medications. Other delayed reactions occur within days to weeks. Immediate and accelerated
Mild: If the penicillin allergy is mild, the use of cephalosporins is reactions include pain at sites of IM injection, reactions are mediated by immunoglobulin E (IgE) antibodies.
probably safe. prolonged (but reversible) sensory and motor
Drug to Drug Interaction: Aminoglycosides. dysfunction following accidental injection into a
For some infections, penicillins are used in combination with an peripheral nerve, and neurotoxicity (seizures,
aminoglycoside (e.g., gentamicin). By weakening the cell wall, the confusion, hallucinations) if blood levels are too
penicillin facilitates access of the aminoglycoside to its intracellular high. Inadvertent intra-arterial injection can
site of action, thereby increasing bactericidal effects. Unfortunately, produce severe reactions—gangrene, necrosis,
when penicillins are present in high concentrations, they interact sloughing of tissue—and must be avoided.
chemically with aminoglycosides and thereby inactivate the
aminoglycoside. Accordingly, penicillins and aminoglycosides should
never be mixed in the same IV solution. Rather, they should be
administered separately. Once a penicillin has been diluted in body
fluids, the potential for inactivating the aminoglycoside is minimal.
Nursing Considerations Related to Penicillin NSG124.05.02.03 Penicillins Preadministration Assessment
Key points: Penicillin is bactericidal. *Advise patients with penicillin Therapeutic Goal
allergy to wear some form of identification (e.g., Medic Alert Treatment of infections caused by sensitive bacteria.
bracelet) to alert emergency healthcare personnel. Amoxicillin Baseline Data
*Instruct outpatients to report any signs of an allergic response The prescriber may order tests to identify the infecting organism and its drug
(e.g., skin rash, itching, hives). Amoxicillin/clavulanate sensitivity. Take samples for microbiologic culture before starting treatment.
Summary: Penicillin agents are bactericidal and are beta-lactam In patients with a history of penicillin allergy, a skin test may be performed to
antibiotics. Many are resistant, and many patients are allergic. determine current allergic status.
Broad spectrum, extended spectrum, and penicillins combined with Ampicillin Identifying High-Risk Patients
a beta-lactamase inhibitor formation increase therapeutic action of Penicillins should be used with extreme caution, if at all, in patients with a
penicillins and decrease resistance. Renal function must be closely history of severe allergic reactions to penicillins, cephalosporins, or
Ampicillin/sulbactam
monitored while patients receive penicillin and should not be carbapenems.
combined with aminoglycosides. Routes
Review Dicloxacillin Penicillins are administered orally, IM, and IV. Before giving a penicillin, make
Sodium Loading: High IV doses of sodium penicillin G can produce sure the preparation is appropriate for the intended route.
sodium overload. Exercise caution in patients under sodium Dosage
restriction (e.g., cardiac patients, those with hypertension). Monitor Nafcillin Doses for penicillin G are prescribed in units (1 unit equals 0.6 mg). Doses for
electrolytes and cardiac status. all other penicillins are prescribed in milligrams or grams.
Hyperkalemia: High doses of IV potassium penicillin G may cause Administration
Oxacillin
hyperkalemia, possibly resulting in dysrhythmias or cardiac arrest. During IM injection, aspirate to avoid injection into an artery. Take care to
Monitor electrolyte and cardiac status. avoid injection into a nerve.
Effects Resulting from Incorrect Injection: Take care to avoid intra- Penicillin G
arterial injection or injection into peripheral nerves because serious
injury can result.
Minimizing Adverse Interactions: Aminoglycosides: When present Penicillin V
in high concentration, penicillins can inactivate aminoglycosides
(e.g., gentamicin). Do not mix penicillins and aminoglycosides in the Piperacillin
same IV solution.
Piperacillin/tazobactam
Except where indicated otherwise, the
implications here apply to all members of the
penicillin family.
Instruct the patient to take oral penicillins with
a full glass of water 1 hour before meals or 2
hours after. Penicillin V,
amoxicillin, and amoxicillin/clavulanate may be
taken with meals.
Instruct the patient to complete the prescribed
course of treatment, even though symptoms
may abate before the full course is over.
Therapeutic Uses: The cephalosporins are broad-spectrum Cephalosporin, Carbapenems, Vancomycin **Vancomycin [Vancocin] is the most widely used antibiotic in U.S. hospitals.
bactericidal drugs with a high therapeutic index. Cephalosporins can **The cephalosporins, carbapenems, and Principal indications are C. difficile infection (CDI), MRSA infection, and the
be useful alternatives for patients with mild penicillin allergy. vancomycin are also antibacterial agents which treatment of serious infections with susceptible organisms in patients allergic
Adverse Reactions: **Cephalosporins may cause pain at sites of IM inhibit the cell wall synthesis of bacteria, and by to penicillins. The major toxicity is renal failure.
injection; patients should be forewarned. Rarely, cephalosporins may disrupting the cell wall, they cause bacterial **Unlike most other drugs discussed here, vancomycin does not contain a
be the cause of pseudomembranous colitis due to colonic lysis and death. beta-lactam ring.
overgrowth with Clostridium difficile. If this superinfection develops, **Cephalosporins and carbapenems are both **Like the beta-lactam antibiotics, vancomycin inhibits cell wall synthesis
the cephalosporin should be discontinued and, if necessary, oral beta-lactam antibiotics like penicillin. and thereby promotes bacterial lysis and death. However, in contrast to the
vancomycin should be given. **Carbapenems are beta-lactam antibiotics beta-lactams, vancomycin does not interact with PBPs. Instead, it disrupts
**Practically all cephalosporins are eliminated by the kidneys; excretion is that have very broad antimicrobial spectra— the cell wall by binding to molecules that serve as precursors for cell wall
by a combination of glomerular filtration and active tubular secretion. One although none is active against MRSA. Four biosynthesis.
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