Antibiotics Flashcards by Tricia Vantino

Approximately what percent of all prescriptions written for antimicrobials are for ambulatory patients diagnosed with upper respiratory tract infections or bronchitis?

21%

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The use of antimicrobial prophylaxis in surgery involves a:

Risk-to-benefit evaluation

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Prophylactic antimicrobials should be
administered intravenously within:

1 hour of surgical incision

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Abx tx is not recommended for longer than?

24 hours

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With a wide therapeutic index and low incidents of side effects, _______________ are the antimicrobials of choice for most surgical procedures

Cephalosporins

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cephalosporin can be safely using patient with an allergic reaction to penicillin that is not?

an IgE-mediated reaction such as anaphylaxis, urticara, bronchospasm
OR
Exfoliative dermatitis (SJS)

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In patients with IgE-mediated reactions to Penicillins, what are alternative abx to use outside of cephalosporins?

Beta-Lactam Abx: Clindamycin or Vancomycin

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Vancomycin is recommended for?

colonization or infection
with methicillin-resistant Staphylococcus aureus or
known IgE-mediated response to β-lactam antibiotics

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What is the most frequent complication of prophylactic antimicrobials, including the IV cephalosporins?

Pseudomembranous colitis

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Adult and Pediatric Dose of Clindamycin

adult 900mg

Peds: 10mg/kg

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Nearly 80% of nosocomial infections occur in what three sites?

Urinary tract
respiratory system
bloodstream

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The incident of nosocomial infections is highly associated with the use of:

devices such as ventilators, vascular access catheters, and urinary catheters

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What are the most common cause of bacteremia or fungemia in hospitalized ?

Intravascular access catheters

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The organism infecting access catheters most commonly comes from the?

Colonized hub or lumen and reflect skin flora such as S. aureus and staphylococcus epidermidis

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Initial therapy of suspected intervascular catheter infection usually includes?

Vancomycin because of the high incidence of methicillin resistant S. aureus and staphylococcus epidermidis in the nosocomial environment

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true or false: most antibiotics cross the placenta and enter maternal milk

true

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The immature fetal liver may lack enzymes necessary to?

Metabolize certain drugs, such such that pharmacokinetics and toxicities in the fetus are different from those and older children and adults

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What is a concern when any drug is administered during early pregnancy?

Teratogenicity

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What antibiotics are contraindicated in pregnancy?

Erythromycin
Fluroquinolones
Nitrofurantoin
Tetracyclines
Trimethoprim

Chloramphenicol
Nalidixic Acid

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How are pharmacokinetics of antimicrobials changed in elderly patient?

Altered oral absorption, distribution, metabolism, and excretion

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True or false: penicillin and cephalosporin do not need significant changes in dosage in elderly patients with normal serum, creatinine concentrations

True

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What are two antibiotics that may require adjustments in dosing regiments in elderly patients?

Aminoglycosides and vancomycin

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How do we reduce the risk of postop infections for HIV infected patients who are at an increased risk for opportunistic infections?

Goal is preoperative control on an anti-retroviral regiment with preserved T4 cell counts

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MOA of Penicillins

the ability of these antimicrobials to interfere with the synthesis of peptidoglycan, which is an essential component of cell walls of susceptible bacteria

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Cell membranes of resistant gram-negative bacteria are in general resistant to?

penicillins because they prevent access to sites where synthesis of peptidoglycan is taking place

What is the antibiotic of choice for treatment of pneumococcal, streptococcal, and meningococcal infections?

Penicillin

What is the drug of choice for treating all forms of actinomycosis and clostridial infections causing gas gangrene?

Penicillin

Prophylactic administration of ____________ is highly effective against streptoccocal infections, accounting for its value in patients with rheumatic fever.

Penicillin

How fast is an intramuscular dose of penicillin excreted?

60-90% is excreted in the first hour via renal excretion

Peak plasma concentration of penicillins decrease how much within one hour after injection?

Decreases to 50% of its peak value within one hour after injection

What is a use of the drug Probenecid? How does it work?

Used to prolong the duration of action of penicillin when given simultaneously. Blocks the renal, tubular secretion of penicillin.

Procaine penicillin contains how much a local anesthetic for every 300,000 units of the antimicrobial?

120mg. Hypersensitivity to procaine must be considered

What is the major mechanism of resistance to the penicillins?

bacterial production of β-lactamase enzymes that hydrolyze the β-lactam ring, rendering the antimicrobial molecule inactive.

Which antibiotics are not susceptible to hydrolysis by Staphylococcal penicillinases?

Methicillin, oxacillin, nafcillin, cloxacillin, and dicloxacillin

Penetration of nafcillin into the central nervous system is sufficient to treat?

staphylococcal meningitis

Broad spectrum penicillin have a wider range of activity than other penicillins being bactericidal against? However, they are all inactivated by?

Gram-positive and gram-negative bacteria penicillinase produced by certain gram-negative and gram-positive bacteria

Which drugs are not effective against most staphylococcal infections?

Penicillin, including broad spectrum, second generation penicillins

Ampicillin has a broader range of activity than?

Penicillin G

Ampicillin covers what microbes?

not only pneumococci, meningococci, gonococci, and various streptococci but also a number of gram-negative bacilli, such as Haemophilus influenzae and Escherichia coli.

Renal function greatly influences the duration of action of Ampicillin since?

Approximately 50% of an oral dose of ampicillin is excreted unchanged by the kidneys in the first 6 hours

Which penicillin is associated with the highest incidence of skin rash, 9% which typically appears 7 to 10 days after initiation of therapy? Often due to?

Ampicillin Often due to protein impurities in the commercial preparation of the drug and do not represent true allergic reactions.

Which anabiotic has an identical spectrum of activity to Ampicillin but is more efficiently absorbed from the G.I. tract and effective concentrations are present in circulation for twice as long?

Amoxicillin

What is another name for third generation penicillin?

extended-spectrum carboxypenicillins

What is a third generation penicillin abx?

Carbenicillin

Carbenicillin is effective at treating?

Infections caused by Pseudomonas aeruginosa and certain Proteus strains that are resistant to ampicillin

How must Carbenicillin be administered?

IV, not absorbed in GI

What may develop in susceptible patients taking Carbenicillin?

CHF in response to acute drug-produced sodium load Hypokalenia and metabolic alkalosis

Carbenicillin interferes with:

normal platelet aggregation such that bleeding time is prolonged but platelet count remains normal

What is another name for fourth generation penicillins?

Extended-Spectrum Acylaminopenicillins

Which penicillins have the broadest spectrum of activity?

Extended-Spectrum Acylaminopenicillins (4th gen penicillins)

What classes of penicillins are derived from Ampicillin?

the carboxypenicillins (3rd gen) and the acylaminopenicillin (4th gen)

Extended-Spectrum Acylaminopenicillins (4th gen penicillins) are ineffective against?

penicillinase-producing strains of S. aureus

What are some Penicillin B-Lactamasa Inhibitor Combinations?

– Clavulanic acid, sulbactam, and tazobactam

MOA of Penicillin B-Lactamasa Inhibitor Combinations

β-lactam compounds that bind irreversibly to the β-lactamase enzymes that are produced by many bacteria, thus inactivating these enzymes and rendering the organisms sensitive to β-lactamase–susceptible penicillins

MOA of Cephalosporins

bactericidal antimicrobials that inhibit bacterial cell wall synthesis and have a low intrinsic toxicity

Like the newer penicillins, the new cephalosporins have?

Broad spectrum antimicrobial action

Nephrotoxicity of cephalosporins is less frequent than when _________________ or __________ are administered

aminoglycosides or polymyxins

What is the cephalosporin that can be nephrotoxic?

cephaloridine

The incidence of allergic reactions in patients being treated with cephalosporins ranges from:

1-10%

The majority of the allergic reactions consist of _________ manifestations that occur ________ hours after drug exposure ?

cutaneous that occur 24 hrs after

Life-threatening anaphylaxis from Cephalosporins is estimated to occur in what percent of patients?

0.02% aka small AF

Are cephalosporins likely to have cross sensitivity within the abx class?

Yes, share immunologic cross reactivity

What is the frequency of cross reactivity between cephalosporins and penicillins?

The possibility of cross-reactivity between cephalosporins and penicillins seems to be very infrequent, and are often used as alternative in patients with a penicillin allergy

If you have an allergy to one penicillin, what is the liklihood of being allergic to another penicillin? Why?

The presence of a common nucleus (β-lactam ring) in the structure of all penicillins means that allergy to one penicillin increases the likelihood of an allergic reaction to another penicillin

Cephalosporins are classified because of their?

Antimicrobial spectrum 1st Gen, 2nd Gen, 3rd Gen

Which cephalosporins can penetrate joints and readily cross the placenta?

ALL

Which generation of cephalosporins are commonly used for prophylaxis in cardiovascular, orthopedic, biliary, pelvic, and intraabdominal surgery? why?

First Generation inexpensive, exhibit low toxicity, and are as active as second- and third-generation against staphylococci and nonenterococcal streptococci.

What is the prototype of 1st Gen Cephalosporins?

Cephalothin

Cephalothin is largely excreted by?

Kidneys, unaltered, emphazing need to renal dose if renal dysfxn

How is Cephalothina administered?

Commonly IV -Oral has poor absorption -IM is painful

Does Cephalothin enter the CSF?

Not in significant amounts so not recommended for tx of meningitis.

__________ has essentially the same antimicrobial spectrum as cephalothin but has the advantage of achieving higher blood levels, presumably due to slower renal elimination.

Cefazolin

What drug is viewed as the drug of choice for antimicrobial prophylaxis for many surgeries? How can it be administered?

Cefazolin IM or IV

__________ and __________ are examples of second-generation cephalosporins with extended activity against ___________ bacteria

Cefoxitin and Cefamandole gram-negative

Which 2nd gen. cephalosporin is resistant to cephalosporinases produced by gram-negative bacteria?

Cefoxitin

Cefamandole is pharmacologically similar to cefoxitin, but poses risks such as? Due to?

poses a risk of bleeding and disulfiram-like reactions with concurrent use of alcohol d/t its methylthiotetrazole side chain

How are 2nd Gen Abx excreted?

predominantly unchanged by the kidneys

Third-generation cephalosporins have an enhanced ability to?

resist hydrolysis by the β-lactamases of many gram-negative bacilli

Which generation of cephalosporins can be used to treat meningitis?

3rd gen. can achieve therapeutic levels in CSF

________________ has the longest elimination half-time of any third-generation cephalosporin and is highly effective against gram-negative bacilli?

Ceftriaxone

Which antimicrobial class is poorly lipid-soluble antimicrobials that are rapidly bactericidal for aerobic gram-negative bacteria

Aminoglycosides

How well are Aminoglycosides absorbed?

Poorly. <1% po absorption

What kind of relationship is sen between plasma creatinine concentration and elimination half-time of aminoglycosides?

Linear Relationship

What are some Aminoglycoside Abx?

Streptomycin Gentamicin Neomycin

Why is streptomycin a rarely selected abx?

because of the rapid emergence of resistant organisms, the frequent occurrence of vestibular damage during prolonged treatment, and the availability of less toxic antimicrobials

Gentamicin is active against?

P. aeruginosa as well as the gram-negative bacilli

When should you add Metronidazole(Flagyl) to your intraoperative abx regimen?

Anytime open bowel, planned or unexpected, occurs.

What can Gentamicin penetrate?

penetrates pleural, ascitic, and synovial fluids in the presence of inflammation

What plasma concentration can cause toxic levels of Gentamicin?

>9mcg/mL

Neomycin is commonly used for?

topical application to treat infections of the skin cornea, and mucous membranes

What are the allergic rxn rates of patients treated with Neomycin?

6-8%

Oral neomycin does not undergo systemic absorption and is thus administered to?

decrease bacterial flora in the intestine before gastrointestinal surgery and as an adjunct to the therapy of hepatic coma.

Side Effects of Aminoglycosides

Ototoxicity Nephrotoxicity Skeletal Muscle Weakness

How do Aminoglycosides cause ototoxicity

drug-induced destruction of vestibular or cochlear sensory hairs that is dose-dependent and most likely occurs with chronic therapy, especially in elderly patients, in whom renal dysfunction is more likely.

What drugs seem to accentuate the ototoxic effects of aminoglycosides?

Furosemide, mannitol, and probably other diuretics

What can aminoglycoside abx's do to the kidneys?

produce acute tubular necrosis that initially manifests as an inability to concentrate urine and the appearance of proteinuria and red blood cell casts. Usually reversible if the drug is d/c

Which aminoglycoside is most nephrotoxic?

Neomycin and therefore not administered by parenteral route