8. Methenamine Hippurate (Hiprex)
Two active components—Methenamine salts which are hydrolysed to formaldehyde and hippuric acid which acidifies the urine
Cochrane review 2012 showed Hiprex is effect in preventing recurrent UTIs
Short term courses (1 week or less) also effective in decreasing number of symptomatic UTIs
Hiprex is ineffective in the background of neurogenic bladders or patients with urinary tract abnormalities
Hiprex is prescribed as 1 g twice a day for adult patients. If the patient has a catheter, this can be increased to three times a day.
8.1 Introduction and Mechanism of Action
The methenamine salts component of Hiprex is excreted in the kidneys, whereupon a process called hydrolysis occurs, forming formaldehyde, a compound with bacteria killing properties.
The Hippuric acid component of Hiprex are also excreted by the kidneys, causing urine to turn acidic, which can either kill or neuter the bacteria within it
The acidic urine also provides the optimal environment to promote and increase the hydrolysis of the methenamine salts.