Methenamine Prescribing Information

Methenamine Description

Each white to off-white capsule shaped tablet contains 1g Methenamine Hippurate, USP which is the Hippuric Acid Salt of Methenamine (hexamethylene tetramine). The tablet also contains inactive ingredients colloidal silicon dioxide, microcrystalline cellulose, magnesium stearate, povidone and sodium starch glycolate.

ACTIONS

Microbiology: Methenamine hippurate tablets has antibacterial activity because the methenamine component is hydrolyzed to formaldehyde in acid urine. Hippuric acid, the other component, has some antibacterial activity and also acts to keep the urine acid. The drug is generally active against E.coli, enterococci and staphylococci. Enterobacter aerogenes is generally resistant. The urine must be kept sufficiently acid for urea-splitting organisms such as Proteus and Pseudomonas to be inhibited.

Susceptibility Testing:

For specific information regarding susceptibility test interpretive criteria and associated test methods and quality control standards recognized by FDA for this drug, please see: https://www.fda.gov/STIC.

Human Pharmacology: Within 1/2 hour after ingestion of a single 1-gram dose of methenamine hippurate, antibacterial activity is demonstrable in the urine. Urine has continuous antibacterial activity when methenamine hippurate is administered at the recommended dosage schedule of 1 gram twice daily. Over 90% of methenamine moiety is excreted in the urine within 24 hours after administration of a single 1gram dose. Similarly, the hippurate moiety is rapidly absorbed and excreted, and it reaches the urine by both tubular secretion and glomerular filtration. This action may be important in older patients or in those with some degree of renal impairment.

Related/similar drugs

amoxicillin, doxycycline, ciprofloxacin, cephalexin, ceftriaxone, Augmentin, levofloxacin

Indications and Usage for Methenamine

Methenamine hippurate tablets, USP is indicated for prophylactic or suppressive treatment of frequently recurring urinary tract infections when long-term therapy is considered necessary. This drug should only be used after eradication of the infection by other appropriate antimicrobial agents.

To reduce the development of drug-resistant bacteria and maintain the effectiveness of methenamine hippurate tablets, USP and other antibacterial drugs, methenamine hippurate tablets, USP should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.

Contraindications

Methenamine hippurate tablets are contraindicated in patients with renal insufficiency, severe hepatic insufficiency, or severe dehydration. Methenamine preparations should not be given to patients taking sulfonamides because some sulfonamides may form an insoluble precipitate with formaldehyde in the urine.

Warnings

Large doses of methenamine (8 grams daily for 3 to 4 weeks) have caused bladder irritation, painful and frequent micturition, albuminuria, and gross hematuria.

Precautions

Prescribing methenamine hippurate tablets in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.

1. Care should be taken to maintain an acid pH of the urine, especially when treating infections due to urea-splitting organisms such as Proteus and strains of Pseudomonas.
   
   
2. In a few instances in one study, the serum transaminase levels were slightly elevated during treatment but returned to normal while the patients were still taking methenamine hippurate tablets, USP. Because of this report, it is recommended that liver function studies be performed periodically on patients taking the drug, especially those with liver dysfunction.
   
   
3. Use in Pregnancy: In early pregnancy the safe use of methenamine hippurate tablets is not established. In the last trimester, safety is suggested, but not definitely proved. No adverse effects on the fetus were seen in studies in pregnant rats and rabbits.
   

Methenamine hippurate tablets taken during pregnancy can interfere with laboratory tests of urine estriol (resulting in unmeasurably low values) when acid hydrolysis is used in the laboratory procedure. This interference is due to the presence in the urine of methenamine and/or formaldehyde. Enzymatic hydrolysis, in place of acid hydrolysis, will circumvent this problem.

Adverse Reactions/Side Effects

Minor adverse reactions have been reported in less than 3.5% of patients treated. These reactions have included nausea, upset stomach, dysuria, and rash.

To report SUSPECTED ADVERSE REACTIONS, contact Jubilant Cadista Pharmaceuticals Inc. at 1-800-313-4623 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Methenamine Dosage and Administration

1 tablet (1.0 g) twice daily (morning and night) for adults and pediatric patients over 12 years of age. 1/2 to 1 tablet (0.5 to 1 g) twice daily (morning and night) for pediatric patients 6 to 12 years of age. Since the antibacterial activity of methenamine hippurate tablets, USP is greater in acid urine, restriction of alkalinizing foods and medications is desirable. If necessary, as indicated by urinary pH and clinical response, supplemental acidification of the urine should be instituted. The efficacy of therapy should be monitored by repeated urine cultures.

How is Methenamine supplied

Methenamine Hippurate Tablets USP, 1 g are white to off-white capsule shaped tablet, debossed with “L” and “59” on one side and break line (functional) on other side.

Bottle pack of 20 tablets with Child Resistant Closure, NDC 59746-797-65
Bottle pack of 100 tablets with Child Resistant Closure, NDC 59746-797-01

Store at 68° to 77°F (20° to 25°C); excursions permitted to 59° to 86°F (15° to 30°C) [See USP Controlled Room Temperature].
Dispense in well-closed, light-resistant container with child-resistant closure.

Rx Only

Distributed by:
Jubilant Cadista Pharmaceuticals Inc.
Salisbury, MD 21801, USA.

Manufactured by:
Unichem Laboratories Limited,
Plot No. 10 to 18, Pilerne Industrial Estate,
Pilerne, Bardez, Goa - 403511, India (IND)

Revision 01/2024

PRINCIPAL DISPLAY PANEL

NDC 59746-797-65

Methenamine
Hippurate Tablets, USP

1 gram

CADISTA

20 Tablets

Rx Only

Each Tablet contains:
Methenamine Hippurate USP 1g.

Usual Dosage: see package
insert for dosage information.

Warning: Keep out of the reach of
children.

Pharmacist: Dispense in well closed,
light-resistant container
with child-resistant closure.

Store at 68° to 77°F (20° to 25°C);
excursions permitted to 59° to 86°F
(15° to 30°C) [See USP Controlled
Room Temperature].

Code: G0/DRUGS/321

Distributed by:
Jubilant Cadista Pharmaceuticals Inc.
Salisbury, MD 21801, USA

Made in India

13015249

NDC 59746-797-01

100 Tablets

13015250