Hippuric acid Methenamine hippurate

Cetalkonium chloride Chlorhexidine digluconate Chloroacetamide Chlorobutanol hemihydrate p-Chloro-m-cresol Chlorothymol Chloroxylenol m-Cresol Disodium undecylenamido MEA-sulfosuccinate Formaldehyde Hexamidine diisethionate 8-Hydroxyquinoline benzoate 8-Hydroxyquinoline sulfate Imidazolidinyl urea Lactic acid Methenamine hippurate Methylparaben Myristalkonium chloride Phenethyl alcohol Phenol... 

Methenamine (hexamethylenetetramine) is an aromatic acid that is hydrolyzed at an acid pH (<6) to liberate ammonia and the active alkylating agent formaldehyde, which denatures protein and is bactericidal. Methenamine is usually administered as a salt of either man-delic (Mandelamine) or hippuric Hiprex, Urex) acid. Not only do these acids acidify the urine, which is necessary to generate formaldehyde, but also, the resulting low urine pH is by itself bacteriostatic for some organisms. 

Methenamine mandelate is the salt of mandelic acid and methenamine and possesses properties of both of these urinary antiseptics. Methenamine hippurate is the salt of hippuric acid and methenamine. Below pH 5.5, methenamine releases formaldehyde, which is antibacterial. Mandelic acid or hippuric acid taken orally is excreted unchanged in the urine, in which these drugs are bactericidal for some gram-negative bacteria when pH is less than 5.5. 

Methenamine mandelate, 1 g four times daily, or methen-amine hippurate, 1 g twice daily by mouth (children, 50 mg/kg/d or 30 mg/kg/d, respectively), is used only as a urinary antiseptic to suppress, not treat, urinary tract infection. Acidifying agents (eg, ascorbic acid, 4-12 g/d) may be given to lower urinary pH below 5.5. Sulfonamides should not be given at the same time because they may form an insoluble compound with the formaldehyde released by methenamine. Persons taking methenamine mandelate may exhibit falsely elevated tests for catecholamine metabolites. 

The action of methenamine mandelate or hippurate is nonspecific against many different microorganisms and consists of the simultaneous effects of formaldehyde and acidity. Microorganisms such as proteus that make a strongly alkaline urine through release of ammonia... 

Methenamine Hippurate, USP. Mcthenamine hippur-aie (Hiprex) is the hippuric acid. salt of mcthenamine. It is readily absorbed after oral administration and is concentrated in the urinary bladder, where it exerts its antibacterial activity. Its activity is increased in acid urine. 

Methenamine is an antiinfective agent. In acidic urine, methenamine is hydrolyzed to ammonia and formaldehyde, which is bactericidal to certain bacteria in urine. Acid salts (methenamine mandelate and hippurate) have some nonspecific bacteriostatic activity and help to maintain low nrine pH. It is indicated in suppression or elimination of bacterinria associated with pyelonephritis, cystitis, and other chronic UTls in treatment of infected residual urine, sometimes accompanying nenrologic disease or diabetes. 

Methenamine is absorbed orally, but 10 to 30% decomposes in the gastric juice unless the drug is protected by an enteric coating. Because of the ammonia produced, methenamine is contraindicated in hepatic insufficiency. Excretion in the urine is nearly quantitative. When the urine pH is 6 and the daily urine volume is 1000 to 1500 mL, a daily dose of 2 g will yield a concennation of 18 to 60 pg/mL of formaldehyde this is more than the MIC for most urinary tract pathogens. Various poorly metabolized acids can be nsed to acidify the urine. Low pH alone is bacteriostatic, so acidification serves a double function. The acids commonly used are mandelic acid and hippuric acid (Uerx, Hiprex). 

Methenamine Hippnrate. Hexamethylenetetramine hippurate Haiprex Hippramine Hiprex Urex [Riker], Urotractan Viapta. C,jH21Ns03 mol wt 319.37. C 56.41%, H 6.63%, N 21.93%, O 15.03%. C jN CjiysiOj. Prepd by refluxing one mole hexamethylenetetramine with one mole hippuric acid in methanol Galat, UJS. pat. 3,004,026 (1959). 

Methenamine (Hiprex) At low urinary pH, is hydrolyzed to formaldehyde which is bactericidal. Formaldehyde kills Gram-negatives, Gram-positives, and funai. Precipitates in presence of sulfonamides. Ammonia produced is somewhat toxic, particularly to the liver. Decrease dose if hepatotoxicity develODS. PO. Conversion to formaldehyde in urine is enhanced by low pH. The acid salts, hippurate or mandelate, help maintain acidic urine. Is not converted to formaldehvde in serum. 

A venerable drug used for the disinfection of acidic urine, methenamine is a low-molecular-weight polymer of ammonia and formaldehyde that reverts to its components under mildly acidic conditions. Formaldehyde is the active antimicrobial component. Methenamine is used for recurrent urinary tract infections. The drug is available in various dosage forms as well as various salts, including the hippurate and mandelate. 

Methenamine and methenamine mandelate are only effective as urinary antisepties if the pH is about 5.5 or lower, when formaldehyde is released. This is normally achieved by giving urinary acidifiers such as ammonium chloride, ascorbic acid, or sodium acid phosphate. In the case of methenamine hippurate, the acidification of the urine is achieved by the presence of hippuric acid. The concurrent use of substances that raise the urinary pH such as acetazolamide, sodium bicarbonate, potassium or sodium citrate is clearly contraindicated. Potassium citrate mixture BPC has been shown to raise the pH by more than 1 at normal therapeutic doses, thereby making the urine sufficiently alkaline to interfere with the activation of methenamine to formaldehyde. Some antacids (containing magnesium, aluminium or calcium as well as sodium bicarbonate mentioned above) can also cause a significant rise in the pH of the urine. ... 

Hippuric acid, compd. with hexamethylene tetramine. See Methenamine hippurate Hippuric acid, o-iodo-, monosodium salt. See lodohippurate sodium HIPS. See Polystyrene, high-impact HiPure Liq. Gelatin, Cosmetic Grade. See Gelatin... 

Fructose Glucose oxidase Glycerin Gum benzoin Hexamidine diisethionate Hydrogenated tallowtrimonium chloride 4-Hydroxybenzoic acid N-Hydroxysuccinic acid Imidazolidinyl urea Isosorbide dinitrate Lactic acid Magnesium salicylate Maleic anhydride Methenamine hippurate Methylparaben... 

---