Methenamine Mandelate

Methenamine mandelate, USP is indicated for the suppression or elimination of bacteriuria associated with pyelonephritis, cystitis, and other chronic urinary tract infections; also for infected residual urine sometimes accompanying neurologic diseases. When used as recommended, methenamine mandelate, USP is particularly suitable for long-term therapy because of its safety and because resistance to the nonspecific bactericidal action of formaldehyde does not develop. Pathogens resistant to other antibacterial agents may respond to methenamine mandelate, USP because of the nonspecific effect of formaldehyde formed in an acid urine. Prophylactic Use Rationale: Urine is a good culture medium for many urinary pathogens. Inoculation by a few organisms (relapse or reinfection) may lead to bacteriuria in susceptible individuals. Thus, the rationale of management in recurring urinary tract infection (bacteriuria) is to change the urine from a growth-supporting to a growth-inhibiting medium. There is a growing body of evidence that long-term administration of methenamine mandelate, USP can prevent the recurrence of bacteriuria in patients with chronic pyelonephritis. T herapeutic Use Rationale: Methenamine mandelate, USP helps to sterilize the urine, and in some situations in which underlying pathologic conditions prevent sterilization by any means, it can help to suppress the bacteriuria. Methenamine mandelate, USP should not be used alone for acute infections with parenchymal involvement causing systemic symptoms such as chi ls and fever. A thorough diagnostic investigation as a part of the overall management of the urinary tract infection should accompany the use of methenamine mandelate, USP.

Contraindicated in renal insufficiency. Methenamine mandelate, USP should not be used in patients who have previously exhibited hypersensitivity to it.

GENERAL PRECAUTIONS Dysuria may occur (usually at higher than recommended dosage). This can be controlled by reducing the dosage and the acidification. When urine acidification is contraindicated or unattainable (as with some urea-splitting bacteria), the drug is not recommended.

An occasional patient may experience gastrointestinal disturbance or a generalized skin rash. Microscopic and rarely gross hematuria have been described.

Formaldehyde and sulfamethizole form an insoluble precipitate in acid urine; therefore, methenamine mandelate, USP should not be administered concurrently with sulfamethizole.

Pregnancy Category C: Animal reproduction studies have not been conducted with methenamine mandelate, USP. It is also not known whether methenamine mandelate, USP can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Methenamine mandelate, USP should be given to a pregnant woman only if clearly needed. Since introduction, published reports on the use of methenamine mandelate, USP in pregnant women have not shown an increased risk of fetal abnormalities from use during pregnancy.