Fluoroquinolones

• What are fluoroquinolones derived from?

  Chloroquine
• What is the first fluoroquinolone used clinically?

  Nalidixic acid
• What is a major problem associated with nalidixic acid?

  It has poor tissue penetration and a narrow antibacterial spectrum
• What are the key substitutions on the fluoroquinolone ring and their effects?

  • Position 6: Fluoro substitution → Increased Gram-negative activity
  • Position 7: Substitution → Increased tissue penetration
  • Position 8: Substitution → Increased antimicrobial activity
• What are the drugs classified as first-generation fluoroquinolones?

  Nalidixic acid
• What is the antimicrobial activity of first-generation fluoroquinolones?

  Effective against Gram-negative bacteria, except Pseudomonas
• What are the special indications for first-generation fluoroquinolones?

  Uncomplicated urinary tract infections (UTIs)
• Name some second-generation fluoroquinolones.

  Norfloxacin, Lomefloxacin, Ofloxacin, Ciprofloxacin
• What is the antimicrobial activity of second-generation fluoroquinolones?

  Effective against Gram-negative bacteria, Pseudomonas, and some Gram-positive bacteria
• What are the special indications for second-generation fluoroquinolones?

  • Urinary tract infections (UTI)
  • Sexually transmitted diseases (STD)
  • Pyelonephritis
  • Prostatitis
  • Skin and soft tissue infections
  • Osteomyelitis
• What are some drugs classified as third-generation fluoroquinolones?

  Levofloxacin, Sparfloxacin, Gatifloxacin, Moxifloxacin
• How does the antimicrobial activity of third-generation fluoroquinolones compare to second-generation?

  It is similar but includes additional coverage for pen-sensitive and pen-resistant Streptococcus pneumoniae
• What are the special indications for third-generation fluoroquinolones?

  • Acute exacerbation of chronic bronchitis
  • Community-acquired pneumonia
• What is the drug classified as a fourth-generation fluoroquinolone?

  Trovafloxacin
• What is the antimicrobial activity of fourth-generation fluoroquinolones?

  Similar to third-generation but with increased anaerobic coverage
• What are the special indications for fourth-generation fluoroquinolones?

  • Same as third-generation, excluding UTIs and pyelonephritis
  • Intra-abdominal infections
  • Pelvic inflammatory disease (PID)
  • Nosocomial pneumonia
• What is the mechanism of action (MoA) of fluoroquinolones?

  They inhibit topoisomerase II (DNA-gyrase) and topoisomerase IV, which are essential for DNA replication
• What is the effect of fluoroquinolones on bacterial cells?

  They are bactericidal and their effectiveness is concentration-dependent
• What are the mechanisms of resistance to fluoroquinolones?

  • Alteration in topoisomerase enzymes
  • Decreased permeability
  • Efflux mechanism
• What is the primary function of DNA strands in bacterial cells?


  They are involved in repairs and replication.
• How do fluoroquinolones affect bacterial cells?

  They are bactericidal and their effectiveness is concentration-dependent.
• What are the mechanisms of resistance to fluoroquinolones in bacteria?

  • Alteration in topoisomerase enzymes
  • Decreased permeability
  • Efflux mechanism
• How are fluoroquinolones absorbed when taken orally?

  They are mostly well absorbed when given on an empty stomach.
• What substances can decrease the absorption of fluoroquinolones?

  Antacids, milk products, and minerals like Al, Mg, Fe, Zn, and Ca.
• What is the protein binding percentage range for fluoroquinolones?

  10-80% (variable).
• What is the elimination route for fluoroquinolones?

  They are eliminated via hepatic, renal, or both pathways.
• What is the typical half-life (T2) range for fluoroquinolones?

  3.5-30 hours (variable).
• What is enterohepatic recycling in relation to fluoroquinolones?

  Some fluoroquinolones undergo enterohepatic recycling.
• What are the therapeutic uses of fluoroquinolones?

  1. Diarrhea (effective against G-ve enteric bacteria)

  • Salmonellosis
  • Shigella
  • Campylobacter

  2. Urinary Tract Infections (UTIs)

  • Effective against gonococcal infections and PID

  3. Soft & Deep Tissue Infections

  • Skin, joints, and bones (osteomyelitis)

  4. Respiratory Infections

  • Haemophilus spp.
  • Streptococcus pneumoniae
  • Anthrax
• Why are fluoroquinolones not strictly urinary antiseptics?

  They have a systemic effect.
• What are some common side effects of fluoroquinolones?

  Arthropathy in children, Achilles tendonitis, crystalluria, GIT disturbances, and photosensitivity.
• What is a serious risk associated with fluoroquinolones in geriatric patients?

  Achilles tendonitis leading to tendon rupture.
• What rare but dangerous side effects are associated with fluoroquinolones?

  Cardiac issues like QT prolongation, CNS effects, hepatotoxicity, hematuria, and aortic aneurysm.
• What drug interactions should be considered with fluoroquinolones?

  • Antacids and milk products decrease absorption.
  • NSAIDs may cause CNS disturbances.
  • Theophylline levels may increase due to fluoroquinolone interaction.
  • Warfarin may increase prothrombin time.
  • Alkalizing agents can lead to crystalluria.