Urinary Tract Anti-Infective Agents

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• Urinary tract anti-infective agents are used to treat bacterial infections of the urinary tract, such as cystitis, pyelonephritis, and urethritis.

• These agents are classified based on their mechanism of action and chemical structure.

1) Quinolones (Fluoroquinolones)

• These drugs act by inhibiting bacterial DNA gyrase and topoisomerase IV, leading to DNA damage and bacterial cell death.

Examples

• Nalidixic Acid

• Norfloxacin

• Enoxacin

• Ciprofloxacin*

• Ofloxacin

• Lomefloxacin

• Sparfloxacin

• Gatifloxacin

• Moxifloxacin

SAR Summary of Quinolones

Position	Structural Feature	SAR Insight
C1	N-substitution (e.g., cyclopropyl, ethyl)	Cyclopropyl enhances Gram-positive activity and broadens spectrum (e.g., ciprofloxacin).
C3 & C4	Carboxylic acid and ketone	Essential for binding to bacterial DNA-topoisomerase complex via Mg²⁺ bridge. Any modification reduces activity.
C5	H or –NH₂ / –OH	Substitutions can enhance Gram-positive activity (e.g., OH improves activity but may increase toxicity).
C6	Fluorine atom (F)	Enhances lipophilicity, cell penetration, and enzyme inhibition. Characteristic of fluoroquinolones.
C7	Piperazine or similar heterocyclic ring	Enhances activity against Gram-negative bacteria. Affects CNS side effects and resistance.
C8	Methoxy or halogen (F, Cl)	Affects phototoxicity and anaerobic activity. Methoxy at C8 (e.g., moxifloxacin) reduces phototoxicity.

2) Miscellaneous Urinary Tract Anti-Infectives

• These agents have varied mechanisms of action, including inhibition of bacterial enzymes, induction of oxidative stress, and acidification of urine, which suppress bacterial growth.

Examples:

• Furazolidone

• Nitrofurantoin*

• Methenamine

  

  
  

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