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Questions and Answers
What is the basis for classifying fluoroquinolones into 'generations'?
What is the basis for classifying fluoroquinolones into 'generations'?
- Their ability to inhibit DNA gyrase
- Their antimicrobial targets (correct)
- Their ability to penetrate porin channels
- Their potency against gram-positive bacteria
What is the primary difference between second-generation and third-generation fluoroquinolones?
What is the primary difference between second-generation and third-generation fluoroquinolones?
- Activity against anaerobic organisms
- Activity against gram-positive bacteria (correct)
- Activity against intracellular infections
- Potency against MRSA
What is the primary mechanism of action of fluoroquinolones?
What is the primary mechanism of action of fluoroquinolones?
- Inhibition of bacterial protein synthesis
- Inhibition of bacterial cell wall synthesis
- Disruption of bacterial membrane integrity
- Inhibition of DNA gyrase and topoisomerase IV (correct)
What is the name of the first quinolone?
What is the name of the first quinolone?
What is a potential consequence of widespread fluoroquinolone use?
What is a potential consequence of widespread fluoroquinolone use?
Which generation of fluoroquinolones is active against anaerobic organisms?
Which generation of fluoroquinolones is active against anaerobic organisms?
What is the mechanism by which fluoroquinolones enter bacterial cells?
What is the mechanism by which fluoroquinolones enter bacterial cells?
What is the primary difference between first-generation and later-generation fluoroquinolones?
What is the primary difference between first-generation and later-generation fluoroquinolones?
Which type of infections are typically treated with fluoroquinolones due to their broad range of coverage?
Which type of infections are typically treated with fluoroquinolones due to their broad range of coverage?
What is the name of the bacterium that causes hemolytic uremic syndrome?
What is the name of the bacterium that causes hemolytic uremic syndrome?
Which of the following fluoroquinolones has poor activity against Streptococcus pneumoniae?
Which of the following fluoroquinolones has poor activity against Streptococcus pneumoniae?
What is the name of the combination of trimethoprim and sulfamethoxazole?
What is the name of the combination of trimethoprim and sulfamethoxazole?
Which of the following is NOT a type of folate antagonist?
Which of the following is NOT a type of folate antagonist?
Which of the following is an indicator of the broad spectrum of coverage of sulfonamides?
Which of the following is an indicator of the broad spectrum of coverage of sulfonamides?
What is the name of the antibiotic that is useful for treating atypical mycobacterial infections?
What is the name of the antibiotic that is useful for treating atypical mycobacterial infections?
Which of the following is NOT a characteristic of fluoroquinolones?
Which of the following is NOT a characteristic of fluoroquinolones?
What is the combination of sulfamethoxazole with trimethoprim effective against?
What is the combination of sulfamethoxazole with trimethoprim effective against?
What is the primary cause of urinary obstructions in patients taking sulfamethoxazole and sulfadiazine?
What is the primary cause of urinary obstructions in patients taking sulfamethoxazole and sulfadiazine?
Which of the following is a rare toxicity of sulfonamides in the hematopoietic system?
Which of the following is a rare toxicity of sulfonamides in the hematopoietic system?
What is the combination of pyrimethamine with sulfadiazine used to treat?
What is the combination of pyrimethamine with sulfadiazine used to treat?
What is the common toxicity of sulfonamides?
What is the common toxicity of sulfonamides?
Which of the following can prevent urinary obstructions caused by sulfamethoxazole and sulfadiazine?
Which of the following can prevent urinary obstructions caused by sulfamethoxazole and sulfadiazine?
What is the condition associated with deficiency of glucose-6-phosphate dehydrogenase activity in RBC?
What is the condition associated with deficiency of glucose-6-phosphate dehydrogenase activity in RBC?
What is the serious skin reaction associated with sulfonamide toxicity?
What is the serious skin reaction associated with sulfonamide toxicity?
What is the pH level at which methenamine decomposes to produce formaldehyde?
What is the pH level at which methenamine decomposes to produce formaldehyde?
Why is methenamine not effective in upper UTIs?
Why is methenamine not effective in upper UTIs?
What is the primary mechanism by which methenamine achieves antibacterial effects?
What is the primary mechanism by which methenamine achieves antibacterial effects?
Why is methenamine contraindicated in patients with hepatic insufficiency?
Why is methenamine contraindicated in patients with hepatic insufficiency?
What is the primary adverse effect of methenamine at higher doses?
What is the primary adverse effect of methenamine at higher doses?
Why is methenamine mandelate contraindicated in patients with renal insufficiency?
Why is methenamine mandelate contraindicated in patients with renal insufficiency?
What is the primary difference between methenamine and nitrofurantoin?
What is the primary difference between methenamine and nitrofurantoin?
What is the primary reason for the contraindication of methenamine in patients with indwelling catheters?
What is the primary reason for the contraindication of methenamine in patients with indwelling catheters?
Which of the following age groups should avoid fluoroquinolones?
Which of the following age groups should avoid fluoroquinolones?
What is a potential cardiac effect of moxifloxacin and other fluoroquinolones?
What is a potential cardiac effect of moxifloxacin and other fluoroquinolones?
Which of the following medications may have its serum levels increased by ciprofloxacin?
Which of the following medications may have its serum levels increased by ciprofloxacin?
What is a limitation of norfloxacin?
What is a limitation of norfloxacin?
What is a characteristic of ciprofloxacin?
What is a characteristic of ciprofloxacin?
What is a potential benefit of ciprofloxacin compared to other antibiotics?
What is a potential benefit of ciprofloxacin compared to other antibiotics?
What is a characteristic of levofloxacin?
What is a characteristic of levofloxacin?
What is a potential use of ciprofloxacin in third-world countries?
What is a potential use of ciprofloxacin in third-world countries?
Study Notes
Fluoroquinolones
- First quinolone: Nalidixic acid, a byproduct of chloroquine synthesis
- Current fluoroquinolones are fluorinated 4-quinolones
- Fluoroquinolones are classified into four generations based on their antimicrobial targets
- First generation: Nalidixic acid, narrow spectrum of susceptible organisms
- Second generation: Ciprofloxacin and norfloxacin, active against aerobic gram-negative, atypical bacteria, and intracellular infections
- Third generation: Levofloxacin, increased activity against gram-positive bacteria
- Fourth generation: Moxifloxacin, active against anaerobic and gram-positive organisms
Mechanism of Action
- Fluoroquinolones enter bacteria through porin channels
- Inhibit DNA gyrase (bacterial topoisomerase II) and bacterial topoisomerase IV
- Prevention of DNA strand breakage
- Articular cartilage erosion (arthropathy) observed in immature animals exposed to fluoroquinolones
Adverse Reactions and DDR
- Moxifloxacin and other fluoroquinolones may prolong the QT interval, contraindicated in patients predisposed to arrhythmias
- Ciprofloxacin may increase serum levels of theophylline, warfarin, caffeine, and cyclosporine
Pharmacology of Select Quinolones
- Norfloxacin: effective against gram-negative and gram-positive organisms, used for treating UTIs, prostatitis, and traveler's diarrhea
- Ciprofloxacin: effective against gram-negative bacilli, used for treating infections caused by Enterobacteriaceae, Pseudomonas aeruginosa, and in respiratory tract infections
- Levofloxacin: effective against gram-positive bacteria, used for treating respiratory tract infections, bone and joint infections, and soft tissue infections
Folate Antagonists
- Inhibitors of folate synthesis: sulfonamides, sulfasalazine, and silver sulfadiazine
- Inhibitors of folate reduction: pyrimethamine, trimethoprim, and cotrimoxazole
- Combination of inhibitors: sulfamethoxazole plus trimethoprim
Sulfonamides
- Analogues of para-aminobenzoic acid
- Broad spectrum of coverage: both gram-positive and gram-negative
- Mechanism of action: inhibits dihydropteroate synthase, preventing folic acid synthesis
Therapeutic Uses
- Urinary tract infections
- Nocardiosis
- Toxoplasmosis
Toxicity/Contraindications
- Urinary tract: crystalluria, urinary obstructions
- Hematopoietic system: acute hemolytic anemia, agranulocytosis, and aplastic anemia
- Hypersensitivity reactions: skin and mucous membrane manifestations, Stevens-Johnson syndrome, and toxic epidermal necrolysis
- Miscellaneous reactions: nausea, anorexia, and vomiting
Methenamine
- Mechanism of action: decomposes at acidic pH in the urine, producing formaldehyde, which is toxic to most bacteria
- Antibacterial spectrum: primarily used for chronic suppressive therapy, effective against lower UTIs
- Pharmacokinetics: administered orally, distributed throughout the body fluids, eliminated in the urine
- Adverse effects: gastrointestinal distress, albuminuria, hematuria, and rashes
Nitrofurantoin
- Narrow antimicrobial spectrum and toxicity
- Less commonly employed for treating UTIs
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Description
This quiz covers the basics of quinolones, folic acid antagonists, and urinary tract antiseptics, including their generations and types.
