Pharmacology Quiz: Quinolones and Antibiotics
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Questions and Answers

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?

  • 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?

  • 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?

    <p>Nalidixic acid</p> Signup and view all the answers

    What is a potential consequence of widespread fluoroquinolone use?

    <p>Increased susceptibility to Clostridium difficile infection</p> Signup and view all the answers

    Which generation of fluoroquinolones is active against anaerobic organisms?

    <p>Fourth generation</p> Signup and view all the answers

    What is the mechanism by which fluoroquinolones enter bacterial cells?

    <p>Through porin channels</p> Signup and view all the answers

    What is the primary difference between first-generation and later-generation fluoroquinolones?

    <p>Presence or absence of fluorination</p> Signup and view all the answers

    Which type of infections are typically treated with fluoroquinolones due to their broad range of coverage?

    <p>Bone, joint, and soft tissue infections</p> Signup and view all the answers

    What is the name of the bacterium that causes hemolytic uremic syndrome?

    <p>E. coli</p> Signup and view all the answers

    Which of the following fluoroquinolones has poor activity against Streptococcus pneumoniae?

    <p>Ofloxacin</p> Signup and view all the answers

    What is the name of the combination of trimethoprim and sulfamethoxazole?

    <p>Cotrimoxazole</p> Signup and view all the answers

    Which of the following is NOT a type of folate antagonist?

    <p>Ciprofloxacin</p> Signup and view all the answers

    Which of the following is an indicator of the broad spectrum of coverage of sulfonamides?

    <p>Their ability to cover both Gram-positive and Gram-negative bacteria</p> Signup and view all the answers

    What is the name of the antibiotic that is useful for treating atypical mycobacterial infections?

    <p>Ciprofloxacin</p> Signup and view all the answers

    Which of the following is NOT a characteristic of fluoroquinolones?

    <p>They are effective against anaerobes</p> Signup and view all the answers

    What is the combination of sulfamethoxazole with trimethoprim effective against?

    <p>Urinary tract infections</p> Signup and view all the answers

    What is the primary cause of urinary obstructions in patients taking sulfamethoxazole and sulfadiazine?

    <p>Crystallization in acid urine</p> Signup and view all the answers

    Which of the following is a rare toxicity of sulfonamides in the hematopoietic system?

    <p>All of the above</p> Signup and view all the answers

    What is the combination of pyrimethamine with sulfadiazine used to treat?

    <p>Toxoplasmosis</p> Signup and view all the answers

    What is the common toxicity of sulfonamides?

    <p>Nausea and anorexia</p> Signup and view all the answers

    Which of the following can prevent urinary obstructions caused by sulfamethoxazole and sulfadiazine?

    <p>Both A and B</p> Signup and view all the answers

    What is the condition associated with deficiency of glucose-6-phosphate dehydrogenase activity in RBC?

    <p>Acute hemolytic anemia</p> Signup and view all the answers

    What is the serious skin reaction associated with sulfonamide toxicity?

    <p>Both A and B</p> Signup and view all the answers

    What is the pH level at which methenamine decomposes to produce formaldehyde?

    <p>pH 5.5 or less</p> Signup and view all the answers

    Why is methenamine not effective in upper UTIs?

    <p>Because the urine pH is not acidic enough to produce formaldehyde</p> Signup and view all the answers

    What is the primary mechanism by which methenamine achieves antibacterial effects?

    <p>By producing formaldehyde, which is toxic to most bacteria</p> Signup and view all the answers

    Why is methenamine contraindicated in patients with hepatic insufficiency?

    <p>Because elevated levels of circulating ammonium ions would be toxic to the CNS</p> Signup and view all the answers

    What is the primary adverse effect of methenamine at higher doses?

    <p>Albuminuria, hematuria, and rashes</p> Signup and view all the answers

    Why is methenamine mandelate contraindicated in patients with renal insufficiency?

    <p>Because mandelic acid may precipitate</p> Signup and view all the answers

    What is the primary difference between methenamine and nitrofurantoin?

    <p>Methenamine is less commonly employed for treating UTIs, while nitrofurantoin is more commonly used</p> Signup and view all the answers

    What is the primary reason for the contraindication of methenamine in patients with indwelling catheters?

    <p>Because methenamine should not be used in patients with indwelling catheters</p> Signup and view all the answers

    Which of the following age groups should avoid fluoroquinolones?

    <p>Pregnant women and children under 18 years of age</p> Signup and view all the answers

    What is a potential cardiac effect of moxifloxacin and other fluoroquinolones?

    <p>Prolongation of the QT interval</p> Signup and view all the answers

    Which of the following medications may have its serum levels increased by ciprofloxacin?

    <p>All of the above</p> Signup and view all the answers

    What is a limitation of norfloxacin?

    <p>It is not effective in systemic infections</p> Signup and view all the answers

    What is a characteristic of ciprofloxacin?

    <p>It is effective against Pseudomonas aeruginosa</p> Signup and view all the answers

    What is a potential benefit of ciprofloxacin compared to other antibiotics?

    <p>It is less toxic than the aminoglycosides</p> Signup and view all the answers

    What is a characteristic of levofloxacin?

    <p>It is an isomer of ofloxacin</p> Signup and view all the answers

    What is a potential use of ciprofloxacin in third-world countries?

    <p>Treating typhoid fever</p> Signup and view all the answers

    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.

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