drugs for urinary antiseptics
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urinary antiseptics methenamine nitrofurantoin pharmacology indications guidelines
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methenamine AND urinary tract infection
Urinary antiseptics are drugs that attain antibacterial activity mainly in urine, so they are used chiefly for lower urinary tract infection (cystitis) or prevention of recurrent UTI.
| Drug | Main use / key point |
|---|---|
| Nitrofurantoin | Common first-line agent for uncomplicated lower UTI. Avoid for pyelonephritis because tissue and blood concentrations are inadequate. Important adverse effects: GI upset, peripheral neuropathy, pulmonary toxicity/fibrosis with prolonged use, and hemolysis in G6PD deficiency. |
| Methenamine hippurate | Urinary antiseptic for prevention of recurrent UTI, not treatment of an acute systemic infection. Requires acidic urine because it releases bactericidal formaldehyde at urine pH below about 5.5. |
| Methenamine mandelate | Same basic mechanism and use as methenamine hippurate. |
| Fosfomycin | Often grouped with urinary antiseptics in pharmacology texts. Used for uncomplicated cystitis; it inhibits bacterial cell-wall synthesis. |
| Nalidixic acid | Older quinolone historically classified as a urinary antiseptic. Largely obsolete in many settings due to resistance and availability of safer alternatives. |
Exam point: The classic true urinary antiseptics are methenamine hippurate and methenamine mandelate. Many textbooks also discuss nitrofurantoin and fosfomycin under drugs acting predominantly in the urinary tract.
Methenamine is supported for recurrent-UTI prophylaxis, with recent systematic reviews including PMIDs 39955521 and 37986168. Nitrofurantoin labeling specifically states it is not indicated for pyelonephritis or perinephric abscess, as described in the DailyMed prescribing information.
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