59 Questions
Which generation of quinolones does ciprofloxacin belong to?
Second generation
What common feature do quinolone carboxylic acids derived drugs share?
Fluorine group
Which quinolone carboxylic acid derivative is considered a first-generation drug?
Nalidixic acid
In which species is pradofloxacin approved for use in the US?
Cats
What is the oral bioavailability of ciprofloxacin in cats and horses?
0%–20%
Which organ typically has particularly high concentrations of quinolones?
Kidneys
What is the major route of elimination for most quinolones?
Renal excretion
Which form of administration significantly impacts the bioavailability of fluoroquinolones?
Oral
What is the impact of antacids containing divalent cations on fluoroquinolone bioavailability?
Decreases bioavailability
Which quinolone is metabolized to form ciprofloxacin?
Enrofloxacin
What is the apparent volume of distribution of most quinolones?
Large
Which animal species exhibits exceedingly poor oral bioavailability of ciprofloxacin?
Ruminating cattle
What is the plasma-protein binding of nalidixic acid in horses?
~30%
Which animal exhibits better bioavailability of enrofloxacin that is not affected by feeding?
Horses
What happens when fluoroquinolones accumulate in phagocytic WBCs?
WBCs become more active
What happens to urine concentrations after fluoroquinolone administration?
They often are high for 24 hours
What does the optimal AUC:MIC ratio need to be for efficacy?
Greater than 125
For which organisms is the MIC for E coli very high?
Pseudomonas
What is more commonly targeted by resistance mechanisms in gram-negative bacteria?
DNA gyrase
Which fluoroquinolone has the greatest activity against Pseudomonas spp?
Ciprofloxacin
What is one of the mechanisms of resistance to fluoroquinolones?
Decreased porins
What tends to be resistant to most quinolones?
Obligate anaerobes
Which organisms are the fluoroquinolones active against?
Klebsiella, P aeruginosa, and Enterococcus faecalis
What is the mechanism for cartilage damage caused by high prolonged dosages of quinolones?
Chelation of magnesium in cartilage
What adverse effect of pradofloxacin led to it not being approved for dogs in the US?
Bone marrow suppression
Which toxicity associated with fluoroquinolones may lead to adverse events ranging from neurologic to musculoskeletal to cardiovascular?
Mitotoxicity
What type of drug interaction occurs when antacids or other drugs containing multivalent cations and sucralfate are used concurrently with quinolones?
Gastrointestinal interference
Which drug impairs the efficacy of quinolones if used concurrently for urinary tract infections?
Nitrofurantoin
Which substance's biotransformation do quinolones inhibit, leading to increased serum concentrations that can result in CNS and cardiac toxicity?
Methylxanthines
What may be increased via concurrent administration of cyclosporine with fluoroquinolones, potentially leading to prolonged and toxic plasma concentrations?
Cyclosporine levels
Which laboratory test results may be altered due to quinolone use?
Urine glucose test results
Why are withdrawal times not available for most quinolones in food-producing animals?
Because they are not approved for use in food-producing animals in most countries.
What is prohibited for extralabel drug use in food-producing animal species in the US?
Deviations from the approved dose, treatment duration, frequency, indication, or administration route on the product label.
What do morphological and ultrastructural changes in bacterial cells indicate as per Cushnie et al. (2016)?
Antibacterial mechanism of action
Which agency added a black-box warning for seven fluoroquinolones due to an increased risk of tendinitis and tendon rupture?
US Food and Drug Administration (FDA)
How do modifications to the side chain attached to the nitrogen at position 1 affect potency?
They enhance gram-negative and gram-positive spectra.
What effect does the addition of a fluorine atom at position 6 have?
It enhances the gram-positive spectrum.
How do substitutions on the piperazyl ring at position 7 affect bacterial penetration and potency?
They enhance bacterial penetration and potency.
What is the impact of quinolones in acidic urine pH?
They are much less effective.
What role do topoisomerase II and topoisomerase IV play in bacterial DNA replication?
Both support DNA supercoiling and uncoiling.
How do fluoroquinolones affect cell lysis in the absence of RNA and protein synthesis?
They induce cell lysis less than non-fluoroquinolones.
What are bacterial ghosts?
Bacteria recognizable only as empty cell envelopes.
Which bacteria are primarily associated with a postantimicrobial effect from quinolones?
Gram-negative bacteria
"The drugs are concentration dependent" implies that:
"The drugs' effectiveness depends on their concentration."
How do lower concentrations of fluoroquinolones affect DNA-DNA gyrase complex binding sites?
They occupy single binding sites resulting in single-strand nicking of DNA.
What role do mammalian topoisomerase enzymes play in relation to quinolone inhibition?
Mammalian topoisomerase enzymes are fundamentally different from bacterial gyrase and are not susceptible to quinolone inhibition.
What is the postantimicrobial effect associated with quinolones?
A prolonged antimicrobial effect after administration of quinolones.
What is the recommended plasma drug concentration in relation to the minimum inhibitory concentration (MIC) of the infecting microbe for quinolones?
10 times the MIC
Why should quinolones be considered for use in infections located in tough-to-penetrate tissues?
Because of their lipid solubility and ability to accumulate in phagocytic WBCs
Why are fluoroquinolones prohibited for extralabel use in food-producing animals in the US?
Because they have a high risk of causing retinal degeneration in food-producing animals
What is the risk associated with enrofloxacin at doses of 5 mg/kg or higher in cats?
Greater chance of developing retinal degeneration
What is the consequence of changes in the ABCG2 transporter due to exposure to photoreactive fluoroquinolones?
Generation of reactive oxygen species
What is the likely consequence of rapid IV administration of high doses of enrofloxacin in horses?
Transient neurologic clinical signs including excitability and seizure-like activity
Why should the dose rate and frequency of quinolones be adjusted for the individual animal and the MIC of the infecting organisms?
To achieve targeted Cmax:MIC ratios for susceptible organisms
What is the primary cause of retinal damage and degeneration in cats exposed to fluoroquinolones?
Accumulation of photoreactive fluoroquinolones due to changes in ABCG2 transporter
What is the effect of pharmacological inhibition of ABCG2 in other species when fluoroquinolones are concurrently administered?
Resulting retinal degeneration when fluoroquinolones are concurrently administered
What is the main reason why extralabel use of fluoroquinolones is prohibited in food-producing animals in the US?
Due to concerns about retinal damage and degeneration in food-producing animals
What is a notable adverse effect associated with both ciprofloxacin and moxifloxacin?
Antimicrobial-induced colitis
What is a common outcome observed with enrofloxacin doses >5 mg/kg/day in cats?
Retinal degeneration
Test your knowledge on the pharmacokinetic differences of quinolones in domestic animals, including their administration methods and absorption into the blood. This quiz covers important aspects of quinolone medications for veterinary use.
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