Advanced search

Report side effect

Report a suspected side effect or falsified product to the MHRA Yellow Card scheme.
Go to {yellow_card_logo} site
{arrow_up} Back to top

Methenamine hippurate 1 g tablets

Active Ingredient:
methenamine hippurate
ADVANZ Pharma See contact details
ATC code: 
About Medicine
{healthcare_pro_orange} This information is for use by healthcare professionals
Last updated on emc: 15 Feb 2024
1. Name of the medicinal product

Methenamine hippurate 1 g tablets

2. Qualitative and quantitative composition

One tablet contains Methenamine Hippurate 1 gram.

For the full list of excipients, see section 6.1.

3. Pharmaceutical form


White to off-white, capsule shaped uncoated tablets.

Dimension 18.9 x 7.9 mm.

The tablet can be divided into equal halves.

4. Clinical particulars
4.1 Therapeutic indications

Methenamine Tablets is indicated in the prophylaxis of uncomplicated lower urinary tract infections:

1. As long-term prophylactic therapy after initial treatment with appropriate chemotherapeutic agent of recurrent urinary infections.

2. As long-term therapy in the prevention of recurrent cystitis.

3. To provide prophylaxis in patients with indwelling catheters, urine collector etc. and to reduce the incidence of catheter blockage.

4. To provide prophylaxis against the introduction of infection into urinary tract during instrumental procedures.

5. Asymptomatic bacteriuria.

4.2 Posology and method of administration


Adults: 1 g 2 times a day.

In patients with catheters the dosage may be increased to 1 g three times daily.

Paediatric population:

Children 6-12 years: 0.5 g twice daily.

Children over 12 years: 1 g twice daily.

In cases of alkaline urine pH, supply of acidifying agent could be needed.

Method of administration

For oral administration.

The tablets may be halved or crushed and taken with water if the patient is unable to swallow whole tablets.

4.3 Contraindications

• Hypersensitivity to the active substance or to any of the excipients listed in section 6.1.

• Intolerance or allergic reactions to formalin.

• Renal insufficiency, severe dehydration and gout.

• Hepatic impairment.

• Metabolic acidosis.

• Infection of the kidney.

Methenamine Tablets should not be given concurrently with sulphonamides because of the possibility of crystalluria.

Alkaline agents reduce the effect of methenamine and should be avoided, antacids might cause an increase of urine pH and hence decrease the effect of methenamine.

4.4 Special warnings and precautions for use



This medicine contains less than 1 mmol sodium (23 mg) per tablet, that is to say essentially 'sodium-free'.

4.5 Interaction with other medicinal products and other forms of interaction

Alkaline agents reduce the effect of methenamine and should be avoided, antacids might cause an increase of urine pH and hence decrease the effect of methenamine.

Concurrent use with sulphonamides increases the risk of crystalluria.

Depending on analytical procedure, methenamine might affect the determination of steroid, catecholamine and 5-hydroxyindole acetic acid leading to incorrect results.

4.6 Fertility, pregnancy and lactation


A moderate amount of data on pregnant women (between 300-1000 pregnancies) has not shown signs of malformations or fetal/neonatal toxicity. Animal studies do not indicate reproductive toxicity (see section 5.3). The use of Methenamine Tablets may be considered during pregnancy, if necessary.


Methenamine Hippurate is excreted in human milk, but at therapeutic doses of Methenamine Tablets no effects on the breastfed newborns/infants are anticipated.


There are no human studies regarding fertility and Methenamine Hippurate.

Animal studies do not indicate direct or indirect harmful effects with respect to reproductive toxicity.

4.7 Effects on ability to drive and use machines

Methenamine Tablets has no or negligible influence on the ability to drive and use machines.

4.8 Undesirable effects

Adverse events frequencies are defined as:

Very common (≥ 1/l0)

Common (≥ 1/100 to <1/10)

Uncommon (≥ 1/1000 to <1/100)

Rare (≥ 1/10 000 to <1/1000)

Very rare (<1/10 000)

Not known (cannot be estimated from the available data).

System Organ Class




Not known

Gastrointestinal disorders

Nausea, vomiting

Diarrhoea, abdominal pains

Skin and subcutaneous tissue disorders



Renal and urinary disorders

Irritation of the bladder


Occasionally superinfection with yeast may occur. At high dosage, chemical cystitis leading to dysuria may occur.

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme Website: or search for MHRA Yellow Card in the Google Play or Apple App Store.

4.9 Overdose

Toxicity: 8 g to a 2½ -year old child resulted in moderate intoxication.

Symptoms: Nausea, vomiting, vertigo, tinnitus and metabolic acidosis may occur. Irritating effect on the urinary tract with albuminuria and haematuria.

Treatment: The treatment is symptomatic and supportive, the use of an anti-emetic and drinking copious quantities of water. Bladder symptoms can be treated by the consumption of copious quantities of water and 2-3 teaspoonfuls of bicarbonate of soda.

5. Pharmacological properties
5.1 Pharmacodynamic properties

Pharmacotherapeutic group: urinary antibacterial agent, ATC code: J01XX05

Mechanism of action

Methenamine Tablets contain Methenamine Hippurate, a salt of methenamine and hippuric acid, which is absorbed and excreted rapidly. In acidic environment, methenamine is hydrolyzed to formaldehyde, which, together with hippuric acid mediates the antibacterial effect in urine. Bacteriological studies have shown that the urine has antibacterial effect already 30 minutes after intake of the drug.

Pharmacodynamic effects

Methenamine Tablets is active against microorganisms, which usually causes urinary tract infection, e.g. Eschericha coli and Aerobacter aerogenes. The substance has decreased effect on urea-degrading bacteria, e.g. Pseudomonas and some strains of Proteus. Urea-degrading bacteria hydrolyze the urea to ammonium hydroxide which is basic and increase urinary pH. This results in reduced hydrolysis of methenamine to formaldehyde.

5.2 Pharmacokinetic properties


Methenamine Tablets is readily absorbed from the gastro-intestinal tract and excreted via the kidney.


Plasma concentrations of Methenamine Hippurate reach maximum 1-2 hours after a single dose and decline with a half-life of about 4 hours. The antibacterial effect is noticed 30 minutes after administration of the drug as mentioned in section 5.1. Methenamine recovered in the urine corresponds to about 80% of the dose given.

5.3 Preclinical safety data

Preclinical studies reveal no special hazard for humans.

6. Pharmaceutical particulars
6.1 List of excipients

Colloidal silica


Magnesium stearate

Croscarmellose sodium

6.2 Incompatibilities

Not applicable

6.3 Shelf life

3 years.

6.4 Special precautions for storage

Store in the original package in order to protect from moisture.

6.5 Nature and contents of container

20, 21, 60, 100 and 105 tablets in coloured glass bottles with a white opaque polypropylene screw cap.

Not all pack sizes may be marketed.

6.6 Special precautions for disposal and other handling

Any unused medicinal product or waste should be disposed in accordance with local requirements.

7. Marketing authorisation holder

Mercury Pharmaceuticals Ltd.

Dashwood House,

69 Old Broad Street,

London, EC2M 1QS,

United Kingdom

8. Marketing authorisation number(s)

PL 12762/0552

9. Date of first authorisation/renewal of the authorisation


10. Date of revision of the text


Company image
Dashwood House, 69 Old Broad Street, London, EC2M 1QS, UK
+44 (0)208 588 9131
Medical Information Direct Line
+44 (0)208 588 9131
Medical Information e-mail
[email protected]
Customer Care direct line
+44 (0)208 588 9273