Methenamine -|- Pharmacology Mnemonics - Flash Cards

Methenamine

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Name: Methenamine

Class: UTI Agent

Mech.: Decomposes at pH £5.5 to NH4+ and formaldehyde (bactericidal).

Absorption: Oral very good, but ¯ pH of stomach decomposes lots of the drug. Enteric-coated tablet solves most of problem.

Distribution: Activated 1° in urine.

Metab.: NH4+ production requires fxning liver for excretion. Kidneys only important if methenamine mandelate or hippurate is used.

Excretion, t½: Excreted in urine. NH4+ reduced requires liver for excretion.

Toxicity/S.E.s: GI distress. Long term = rash, hematuria, albuminuria, painful/frequent micturition.

Utility: Chronic suppression of UTIs.

Special Features: No resistance formation. Orgs which raise urine pH inhibit formaldehyde formation ® ¯ sensitivity.