Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.
Quick facts
- How it is given
- oral
- Type
- human prescription drug
- RxNorm ID
- 992153
We do not publish dosing. How much of this medicine to take, how often, and for how long depends on your age, weight, kidney and liver function, other conditions and other medicines. That is a decision for the person who prescribes or dispenses it. Follow the directions on your own pack and ask your pharmacist if anything is unclear.
What it is used to treat
INDICATIONS AND USAGE Methenamine mandelate is indicated for the suppression or elimination of bacteriuria associated with pyelonephritis, cystitis, and other chronic urinary tract infections; also those neurologic diseases leading to an infected residual urine. When used as recommended, methenamine mandelate 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 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 growthsupporting to a growth-inhibiting medium. There is a growing body of evidence that long-term administration of methenamine mandelate can prevent the recurrence of bacteriuria in patients with chronic pyelonephritis. Therapeutic Use Rationale Methenamine mandelate 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 should not be used alone for acute infections with parenchymal involvement causing systemic symptoms such as chills 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.
About this medicine
DESCRIPTION Methenamine mandelate, a urinary antibacterial agent, is the chemical combination of mandelic acid with methenamine. Methenamine mandelate is available for oral use as film-coated tablets. Each Methenamine mandelate 500mg tablet contains the following inactive ingredients: Caramel, Carmine, Croscarmellose Sodium, Magnesium Stearate, Microcrystalline Cellulose, Polyethylene Glycol, Polyvinyl Alcohol, Silicon Dioxide, Spirulina Extract, Talc, Titanium Dioxide. Each Methenamine mandelate 1000mg tablet contains the following inactive ingredients: Croscarmellose Sodium, Ferric Oxide Red, Ferric Oxide Yellow, Magnesium Stearate, Microcrystalline Cellulose, Polyethylene Glycol, Polyvinyl Alcohol, Silicon Dioxide, Talc, Titanium Dioxide.
Who should not take it
CONTRAINDICATIONS Methenamine mandelate tablets are contraindicated in patients with renal insufficiency, severe hepatic disease, severe dehydration, and in patients who have exhibited hypersensitivity to any components of this product.
Warnings
WARNINGS Methenamine mandelate should be avoided in patients with gout because it may precipitate urate crystals in their urine. A similar situation may arise in patients with a predisposition to the formation of uric acid stones. Methenamine preparations should not be given to patients taking sulfonamides because some sulfonamides may form an insoluble precipitate with formaldehyde in the urine.
Reported side effects
ADVERSE REACTIONS Gastrointestinal disturbances (nausea, stomach upset), generalized skin rash, dysuria, painful or difficult urination may occur occasionally with the use of methenamine preparations. Microscopic and rarely, gross hematuria have been described.
Interactions with other medicines
Drug Interactions Formaldehyde and sulfamethizole form an insoluble precipitate in acid urine; therefore, methenamine mandelate should not be administered concurrently with sulfamethizole or other sulfonamides. Concurrent use of salicylates may lead to increased serum salicylate levels since excretion of salicylates is reduced in acidified urine.
If too much is taken
OVERDOSAGE Minimize absorption by inducing vomiting or by gastric lavage followed by administration of activated charcoal. Administer orally fluids and alkalinize with sodium bicarbonate.
Storing it safely
Store at 20° to 25°C (68° to 77°F); excursions permitted to 15° to 30°C (59° to 86°F) [see USP Controlled Room Temperature].
Before you take anything new
Tell your pharmacist or doctor about every medicine you take — including ones bought without a prescription, herbal products and supplements. Interactions are one of the most common avoidable causes of harm from medicines, and a pharmacist can check your full list in a couple of minutes.
This page is built from the openFDA record of the U.S. Food and Drug Administration's approved labelling for this product, effective 26 March 2026. Label text has been shortened and reformatted for readability; safety wording has not been altered in meaning. FDA labelling describes products approved in the United States — brand names, strengths, formulations and approved uses may differ in your country. Always read the leaflet that comes with your own pack. PocketsInfo is not affiliated with, and is not endorsed by, the FDA. Retrieved 2026-07-30.