67 Questions
Which aminoglycosides have broad spectra that include many gram-negative aerobic bacteria as well as synergistic activity toward selected gram-positive organisms?
Neomycin and framycetin
Which of the following pairs correctly match the narrow-spectrum aminoglycosides?
Streptomycin and dihydrostreptomycin
Which aminoglycoside has an extended spectrum that includes Pseudomonas aeruginosa?
Tobramycin
What contributes to the high aqueous solubility and poor lipid solubility of aminoglycoside antimicrobials?
Hydroxyl groups on the sugar moieties
What characteristic is shared by apramycin with other aminoglycosides?
Chemical structure
What is unique about the structure of spectinomycin compared to other aminocyclitols?
Its mechanism of action differs significantly
Which feature of aminoglycosides limits their movement particularly in acidic environments?
Ionization at physiologic pH
What is the primary target site of aminoglycosides within bacteria?
Ribosome
What can markedly reduce the efficacy of aminoglycosides?
Anaerobic environment
Why is transfer into bacteria diminished in hypoxic tissues?
Low oxygen tension
What effect does an alkaline pH have on passive movement of aminoglycosides across bacterial cell membranes?
Facilitation of movement
What is the impact of changes in osmolality on the uptake of aminoglycosides?
Enhanced uptake
Which factor can interfere with the transport of cationic aminoglycosides into bacteria?
Divalent cations in LPS, cell wall, or membrane
In what type of environment are aminoglycosides markedly curtailed in efficacy?
Anaerobic environment
What synergistic effect is commonly observed when aminoglycosides are combined with beta-lactam antimicrobials?
Enhanced cell wall injury and increased uptake of aminoglycosides
Which subunit of the bacterial ribosome is particularly bound by aminoglycosides?
30S ribosomal subunit
What is the most commonly reported adverse effect of aminoglycosides?
Nephrotoxicity
How can kidneys be protected from aminoglycoside toxicity?
Allowing plasma drug concentrations to decrease between doses
Which factor increases the risk of aminoglycoside nephrotoxicosis?
Dehydration and hypovolemia
What is the role of mitochondria in aminoglycoside-induced ototoxicity?
Binding and damage to mitochondria causes ototoxicity
What are some indicators of aminoglycoside nephrotoxicity?
Reduced fractional sodium excretion
How does early nephrotoxicity manifest in animals treated with aminoglycosides?
Polyuria
What effect does aciduria have on the risk of aminoglycoside nephrotoxicosis?
Increases the risk
Which animals are particularly sensitive to the toxic vestibular effects of aminoglycosides at therapeutic concentrations?
Cats
What is one way to decrease toxicity in diurnal animals when administering aminoglycosides?
Administer the dose in the morning
Why should aminoglycosides not be administered topically into the ear if the tympanic membrane is not intact?
To prevent vestibular injury
What is the role of once-daily dosing in enhancing the efficacy and safety of aminoglycosides?
It helps maintain high drug concentrations above MIC.
Which bacteria are more resistant to aminoglycosides when in an anaerobic environment?
Enterobacteria
Which of the following is NOT a mechanism of resistance to aminoglycosides?
Decreased pH
In which bacteria is adaptive resistance most frequently observed?
Pseudomonas aeruginosa
What is the reason behind the limited efficacy of streptomycin and dihydrostreptomycin in bacterial infections?
Narrow spectrum
Which of the following aminoglycosides is considered to have the broadest spectrum?
Amikacin
What effect does increased production of the outer cell membrane protein, H1, have on Pseudomonas aeruginosa's resistance?
Leads to resistance against gentamicin
Which bacteria are still susceptible to streptomycin and dihydrostreptomycin despite their limited efficacy?
Mycobacterium tuberculosis
What happens to adaptive resistance if bacterial cells survive the initial ionic binding of aminoglycosides?
It persists even after multiple dosing
How does neomycin differ from streptomycin in terms of clinical use?
Neomycin has a broader spectrum targeting gram-negative bacteria.
What factor can affect the elimination of aminoglycosides?
Age
How do aminoglycosides typically follow elimination kinetics?
Three-compartment model
What percentage of injected aminoglycosides is excreted unchanged via the kidneys during the beta phase of elimination?
90%
How does the terminal elimination half-life typically vary with the volume of the extracellular fluid compartment?
Increases proportionately
What is the main focus when altering a dosage regimen of aminoglycosides?
Monitoring plasma concentrations
Why are aminoglycosides commonly used despite their potential for nephrotoxicity?
Broad-spectrum activity
How is the dosing frequency typically adjusted for aminoglycosides in concentration-dependent situations?
Increase both dose rate and frequency
In cases of renal failure, what should be done with the treatment interval for aminoglycosides?
Increased
'Trough concentrations' generally refer to sampling what part of the dosing cycle?
Just before dosing
Why are aminoglycosides administered once daily at high doses?
To minimize the risk of nephrotoxicity
Which of the following factors increases the risk of vestibular and cochlear damage?
Treatment with gentamicin
What is the order of aminoglycosides from most to least potent for neuromuscular effects?
Neomycin, amikacin, kanamycin, gentamicin, tobramycin
Which drug has been found to have the least ototoxic potential among aminoglycosides?
Netilmicin
What can antagonize the neuromuscular blockade caused by aminoglycosides?
Neostigmine
Which of the following drugs is associated with causing enhanced nephrotoxicity when administered concurrently with aminoglycosides?
Loop-acting diuretics
What is a noteworthy laboratory finding associated with aminoglycosides?
Elevated BUN levels
What is the mechanism of action that makes aminoglycosides relatively ineffective against facultative anaerobes in a low-oxygen environment?
Requirement for active transport using oxygen
Which route of administration allows for nearly complete absorption of aminoglycosides?
Intramuscular (IM)
Why are short dosing intervals, including continuous infusions, contraindicated for aminoglycosides?
To prevent accumulation and toxicity
Where do aminoglycosides accumulate increasingly due to ionization?
Kidneys
What is the main route of excretion for aminoglycosides?
Renal excretion
In which fluids are effective concentrations NOT reached when administering aminoglycosides?
CSF
Why are aminoglycosides not administered with short dosing intervals?
To minimize adaptive resistance
In the presence of enteritis and other pathological changes, absorption of aminoglycosides may be:
Increased
What characterizes the route of absorption after subcutaneous (SC) injection of aminoglycosides?
Protracted
What is the elimination half-life of apramycin in calves?
~4–5 hours
Which bacterial species is apramycin NOT active against?
Streptococci
How is spectinomycin primarily eliminated from the body?
Via glomerular filtration
In which species is apramycin considered toxic?
Cats
What is the dosing regimen for spectinomycin in dogs when administered orally?
5–11 mg/kg, PO, every 12 hours for 4 days
What is the primary effect of spectinomycin on bacterial ribosomes?
Bacteriostatic effect
Test your knowledge on factors increasing the risk of vestibular and cochlear damage, including preexisting impairments, concurrent ototoxic drugs, and the varying ototoxic potential of different aminoglycosides. Learn about the protective effects of N-acetylcysteine in reducing the risk of aminoglycoside-induced ototoxicity.
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