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27 Cards in this Set

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Question: What is the MOA of gentamicin, and other aminoglycosides?
They are bactericidal inhibitors, by binding to 30S and inhibit the formation of the initiation complex while also causing mRNA misreading, and inhibit translocation.
Aminoglycosides are dependent on what and therefore, are ineffective against what?
They are dependent on oxygen for uptake into bacterial cell; therefore, they are ineffective against anaerobes.
Gentamicin, tobramycin, and amikacin are important drugs against?
Aerobic gram-negative bacteria (E. coli, Enterobacter, Kelbsiella, Proteus, Providencia, Pseudomonas, and Serratia.
Streptomycin is used to treat?
With combination of penicillin, os more effective in enterococcal carditis than other aminoglycosides. Tuberculosis, plaque, and tularemia.
Due to neomycin toxicity, it is restricted to?
Bowel surgery (kills bowel flora; therefore, reducing chance of infection) and topical use.
What are the toxicity associated with aminoglycosides.
Nephrotoxicity (especially with amphotericin BH, vancomycin, or cephalosporin) and ototoxicity (esp. with loop diuretic); and teratogen.

Rare curare-like effect (neuromusclar blockade--muscle paralysis and apnea)

Always follow PT's BUN and creatinine levels.
Question: A 70 kg PT with creatinine clearance of greater than 80 mL/min has a gram-negative infection. Amikacin is administered intramuscularly at a dose of 5 mg/kg every 8 hours, and the PT begins to respond. After 2 days, creatinine clearance declines to 30 mL/min. Assuming that no information is available about amikacin plasma levels, what would be the most reasonable approach to management of the PT at this point?
Decrease the dosage to 120 mg every 8 hours. Because creatinine clearance is only one third of the starting value, a dose reduction should be made to one third of that given initially.
Aminoglycosides are often used synergistically with what?
Gentamicin with ampicillin or vancomycin to treat enterococcal endocarditis.

Aminoglycosides with cephalosporins to treat life-threatening bacterial infections.
Question: What is a correct statement about bacterial resistance to aminoglycosides?
Clinical resistance mainly occurs through plasmid mediated formation of group transferase enzymes.
Question: Which antibiotic is the most effective agent in the treatment of an infection due to enterococci if used in combination with penicillin G?

Out of: amikacin, gentamicin, neomycin, neomycin, spectinomycin, streptomycin
Streptomycin. About 15% of enterococcal isolates that are resistant to gentamicin and other systemic aminoglycosides remain susceptible to streptomycin.
Question: Regarding the antibacterial action of gentamicin, what is a correct statement?
Antibacterial action of aminoglycosides is concentration-dependent rather than time-dependent. When the plasma level of gentamicin falls below the minimal inhibitory concentration, the drug continues to exert antibacterial effects for several hours--a postantibiotic effect.

Note: this explains the administration of a single large does instead of multiple smaller doses.
Question: An adult PT weights 70 kg, has bacteremia, suspected from a gram-negative rod. Tobramycin is administered once a day, and the loading dose must be calculated to achieve a peak plasma level of 20 mg/L. Assume normal renal function. Vd = 20 L; T 1/2 = 3 h; CL = 80 mL/min. What loading dose should be given?
400 mg. LD = plasma concentration x volume distribution.
Question: What drug is most likely to be effective against multi-drug-resistant strains of M. tuberculosis, including those resistant to streptomycin.
Amikacin. Treatment of TB, amikacin or streptomycin are always used in combination with other antitubercular agents.
Question: A 67 yo man is seen complaining of pain in and behind the right hear. There is edema of external otic canal with purulent exudate and weakness of the muscles on the right side of face. Pt is diabetic. Gram stain of exudate shows polymorphonucleocytes and gram-negative rods. Diagnosis is external otitis. What is the appropriate plan?
The PT should be hospitalized and treatment started with gentamicin plus ticarcillin.

Likely pathogens include E. coli and Pseudomonas aeruginosa, and coverage must include other gram-negative rods. Combination of aminoglycoside plus a wider spectrum penicillin is must suitable for pseudomonas strains.
Question: Regarding the toxicity of gentamicin, what is correct?
More nephrotoxic effects than ototoxicity. Ototoxicity is irreversible, which increases by loop diuretics.
Question: What is true about neomycin?
Used in hepatic coma, to decrease protein intake and suppress coliform bacteria; therefore, reducing ammonia intoxication.

Also, used for sterilization prior to bowel surgery.
Streptomycin is the DOC for?
Plaque, tularemia, adjunctive value in TB.
Question: This drug has pharmacodynamic and pharmacokinetic properties almost identical to those of gentamicin, but has poor activity in combination with penicillin against enterococci.
Tobramycin, and must less effective than either gentamicin or streptomycin when used in combination with penicillin or vancomycin for enterococcal endocarditis.
Question: Your 23 year old female PT is pregnant and has gonorrhea. The medical history includes anaphylaxis following exposure to amoxicillin. Worried about compliance, you would like to treat this PT with a single dose, so you choose?
Spectinomycin.

Avoid cephalosporins in PTs with history of hypersensitivity to penicillins; avoid fluoroquinolones in pregnancy.
In the empiric treatment of severe bacterial infections of unidentified etiology, this drug, often used in combination with an aminoglycoside, provides coverage against many staphylococci.
Nafcillin or cephalosporin.
Question: Which statement about "once-daily" dosing with aminoglycosides is accurate?
Convenient for outpatient therapy; often less toxic; less nursing time; under dosing is less of a problem. AND, is important for appropriate dose in PTs with renal insufficiency.

Aminoglycosides are eliminated by the kidneys.
Aminoglycosides must diffuse across the cell wall; therefore, they are often used with what that helps breaks down the wall to facilitate diffusion?
Penicillin.
Most aminoglycosides end in?
-mycin.
Owing to their polar nature, aminoglycosides are not?
Absorbed after oral administration.
Netilmycin is more likely to be effective than streptomycin in the treatment of?
Hospital-acquired infection caused by Serratia marcescens.
Because of what risk, streptomycin should not be used when other drugs will serve?
Ototoxicity.
Spectinomycin is used for?
Its sole purpose is to be used as a backup drug, most commonly in those who are allergic to beta-lactams.