Urinary Antiseptics

URINARY ANTISEPTICS


URINARY ANTISEPTICS

  • Oral drugs rapidly excreted via urine.
  • Suppresses bacterial growth in urinary tract.
  • More effective in acidic urine, – Due to low pH being an independent bacterial growth inhibitor.

Important urinary antiseptics:

  • Nitrofurantoin, methenamine mandelate & nalidixic acid.

Individual drug description:

1. Nitrofurantoin:

  • Active against most urinary pathogens, except Pseudomonas & Proteus.
  • Develops slow resistance.
  • Used infrequently.
  • MOA: 
    • Allows bacterial enzymes to act itself –> results in reduction of nitrofurantoin –> DNA damage.
  • Adverse effects: 
    • Diarrhea, phototoxicity, neurotoxicity, peripheral neuropathy & hemolysis in G-6-PD deficient patients.

2. Methenamine Mandelate:

  • Mandelate salt is used – Itself a urine acidifying agent.
  • Ineffective against Proteus – Due to NH release –> alkalinizing urine.
  • MOA:
    • Methenamine release formaldehyde at low pH (below 5.5).
    • Formaldehyde contributes to its antibacterial activity.
  • Contraindication:
    • Combination with sulfonamides.
    • Due to insoluble complex formation between formaldehyde & sulfonamides.

3. Nalidixic acid:

  • A quinolone drug.
  • MOA:  
    • Acts by inhibiting DNA gyrase.
    • Ineffective against pseudomonas & proteus.
    • Resistance emerges rapidly.
  • Adverse effect:
    • Neurotoxicity (major).

NOTE:

  • Phenazopyridine:
  • Has analgesic property & useful for alleviating symptoms of dysuria, frequency, burning & urgency.
  • Not a urinary antiseptic.

Exam Important

  • Urinary antiseptics suppresses bacterial growth in urinary tract.
  • Urinary antiseptics are particularly more effective in acidic urine, because of their low pH being an independent bacterial growth inhibitor.
  • Important urinary antiseptics include Nitrofurantoin, methenamine mandelate & nalidixic acid.
  • Nitrofurantoin is active against most urinary pathogens, except Pseudomonas & Proteus.
  • Infrequently used urinary antiseptic is Nitrofurantoin.
  • Adverse effects of nitrofurantoin include diarrhea, phototoxicity, neurotoxicity & hemolysis in G-6-PD deficient patients.
  • Mandelate salt is used itself a urine acidifying agent.
  • Methenamine Mandelate is ineffective against Proteus, due to NH release which alkalinizes urine.
  • Methenamine release formaldehyde at low pH (below 5.5), which contributes to its antibacterial activity.
  • Methenamine Mandelate is contraindicated in combination with sulfonamides, due to its insoluble complex formation between formaldehyde & sulfonamides.
  • Nalidixic acid is a quinolone drug.
  • Nalidixic acid acts by inhibiting DNA gyrase & are ineffective against pseudomonas & proteus.
  • Neurotoxicity is the major adverse effect of nalidixic acid.
  • Phenazopyridine has analgesic property & useful for alleviating symptoms of dysuria, frequency, burning & urgency, but is not a urinary antiseptic drug.
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