Consumer medicine information

Chemists' Own Urinary Tract Antibacterial 1000mg Tablets

Methenamine hippurate

BRAND INFORMATION

Brand name

Chemists' Own Urinary Tract Antibacterial

Active ingredient

Methenamine hippurate

Schedule

Unscheduled

 

Consumer medicine information (CMI) leaflet

Please read this leaflet carefully before you start using Chemists' Own Urinary Tract Antibacterial 1000mg Tablets.

SUMMARY CMI

CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL 1000mg Tablets

Consumer Medicine Information (CMI) summary

The full CMI on the next page has more details. If you are worried about using this medicine, speak to your doctor or pharmacist.

1. Why am I using CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL?

CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL contains the active ingredient methenamine hippurate. CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL helps prevent or slow the growth of bacteria that cause urinary tract infections so that they occur less frequently.

For more information, see Section 1. Why am I using CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL? in the full CMI.

2. What should I know before I use CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL?

Do not use if you have ever had an allergic reaction to methenamine hippurate or any of the ingredients listed at the end of the CMI.

Talk to your doctor or pharmacist if you have any other medical conditions, take any other medicines, or are pregnant or plan to become pregnant or are breastfeeding.

For more information, see Section 2. What should I know before I use CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL? in the full CMI.

3. What if I am taking other medicines?

Some medicines may interfere with CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL and affect how it works.

A list of these medicines is in Section 3. What if I am taking other medicines? in the full CMI.

4. How do I use CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL?

  • Adults and children 12 years or older: One tablet twice daily with or without food.
  • Not recommended for children under 12 years of age.

More instructions can be found in Section 4. How do I use CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL? in the full CMI.

5. What should I know while using CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL?

Things you should do
  • See your doctor if signs and symptoms of urinary tract infection appear, including pain and difficulty in passing urine, blood in urine, pain or discomfort in the lower abdomen.
  • Tell your pharmacist or doctor if you are taking any other medicines.
  • Tell your pharmacist or doctor if there are changes to your diet, health or medical condition or if you feel unwell or experience side effects.
Things you should not do
  • Do not take CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL to treat any other conditions unless your doctor or pharmacist tells you to.
  • Do not take more than the recommended dose unless your doctor pharmacist tells you to.
  • Do not give CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL to anyone else, even if they have the same condition as you.
  • Do not use this medicine in children under 12 years of age.
Driving or using machines
  • Using this product is not known to affect your ability to drive or to use machines.
Looking after your medicine
  • Keep your tablets in its original container until it is time to take them.
  • Keep it in a cool dry place away from moisture, heat or sunlight where the temperature stays below 25°C.
  • Do not store it in the bathroom or near a sink, or in the car or on window sills.
  • Keep it where children cannot reach it.

For more information, see Section 5. What should I know while using CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL? in the full CMI.

6. Are there any side effects?

The most common side effects of CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL are nausea (feeling sick), vomiting (upset stomach), painful urination, rash, diarrhea (loose bowel), and pain round the abdomen.

Most side effects of CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL are mild and do not last long but if they persist, bother you or are signs of an allergy, talk to your pharmacist or doctor or go to Accident and Emergency at your nearest hospital.

For more information, including what to do if you have any side effects, see Section 6. Are there any side effects? in the full CMI.



FULL CMI

CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL 1000mg Tablets

Active ingredient(s): Methenamine hippurate

Consumer Medicine Information (CMI)

This leaflet provides important information about using CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL. You should also speak to your doctor or pharmacist if you would like further information or if you have any concerns or questions about using CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL.

Where to find information in this leaflet:

1. Why am I using CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL?
2. What should I know before I use CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL?
3. What if I am taking other medicines?
4. How do I use CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL?
5. What should I know while using CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL?
6. Are there any side effects?
7. Product details

1. Why am I using CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL?

CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL contains the active ingredient methenamine hippurate, which has an antibacterial action against bacteria in the urine that cause urinary tract infections.

CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL helps prevent or slow the growth of bacteria that cause urinary tract infections so that they occur less frequently.

2. What should I know before I use CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL?

Warnings

Do not use CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL if:

  • you are allergic to methenamine hippurate, formaldehyde or any of the ingredients listed at the end of this leaflet.
    Always check the ingredients to make sure you can use this medicine.
    Some of the symptoms of an allergic reaction may include:
    - shortness of breath
    - wheezing or difficulty breathing
    - swelling of the face, lips, tongue or other parts of the body
    - rash, itching or hives on the skin
  • you are severely dehydrated.
  • you have serious problems with your kidneys and liver.
  • you have gout.
  • you have a condition called metabolic acidosis (a chemical imbalance in the blood)

Check with your doctor or pharmacist if you:

  • are unsure whether the above conditions apply to you.
  • have any other medical conditions such as gout, metabolic acidosis, kidney or liver problems.
  • take any medicines for any other condition
  • use catheter to pass urine or help with incontinence.

During treatment, you may be at risk of developing certain side effects. It is important you understand these risks and how to monitor for them. See additional information under Section 6. Are there any side effects?

Pregnancy and breastfeeding

Check with your doctor or pharmacist if you are pregnant or intend to become pregnant.

Talk to your doctor or pharmacist if you are breastfeeding or intend to breastfeed.

Your doctor or pharmacist will discuss the benefits and possible risks of taking the medicine during pregnancy.

3. What if I am taking other medicines?

Tell your doctor or pharmacist if you are taking any other medicines, including any medicines, vitamins or supplements that you buy without a prescription from your pharmacy, supermarket or health food shop.

Some medicines may interfere with CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL and affect how it works.

  • Sulphonamides: Some sulphonamides may form an insoluble crystalline precipitate with formaldehyde in urine, therefore concurrent administration with CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL should be avoided.
  • Alkalising agents: Do not take this medicine with other products that make your urine less acidic such as acetazolamide or potassium citrate; since these can make CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL less effective.

Check with your doctor or pharmacist if you are not sure about what medicines, vitamins or supplements you are taking and if these affect CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL.

4. How do I use CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL?

The label on your pack of CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL will tell you how to take your medicine and how often.

If you do not understand the instructions on the pack, ask your doctor or pharmacist for help.

How much to take

  • Adults and children 12 years or older: One tablet twice daily.
  • Not recommended for children under 12 years of age.
  • Do not exceed the recommended dosage.

When to take CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL

  • CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL should be used twice daily with or without food.
  • A glass of water, milk or juice may help you swallow the tablet.

How long to take CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL

Continue taking your medicine for as long as your doctor or pharmacist tells you.

This medicine helps to control your condition, but does not cure it.

If you forget to take CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL

If you forget to take CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL tablets, do not take a double dose to make up for the missed dose. Simply take your next dose as planned.

If you use too much CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL

If you think that you have used too much CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL, you may need urgent medical attention.

You should immediately:

  • phone the Poisons Information Centre
    (by calling 13 11 26), or
  • contact your doctor, or
  • go to the Emergency Department at your nearest hospital.

You should do this even if there are no signs of discomfort or poisoning.

5. What should I know while using CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL?

Things you should do

  • See your doctor if signs and symptoms of urinary tract infection appear, including pain and difficulty in passing urine, blood in urine, pain or discomfort in the lower abdomen. You may need to have your urine tested and given antibiotics to treat the infection. Your doctor will advise you if and when you can take CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL again.
  • Tell your pharmacist or doctor if you are taking any other medicines, including any that you get without a prescription from your pharmacy, supermarket or health food shop.
  • Tell your pharmacist or doctor if there are changes to your diet, health or medical condition, what treatment you receive including medicines such as CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL, you start to use catheters for incontinence, or if you feel unwell or experience side effects.

Remind any doctor, dentist or pharmacist you visit that you are using CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL.

Things you should not do

  • Do not take CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL to treat any other complaints unless your doctor tells you to.
  • Do not take more than the recommended dose unless your doctor pharmacist tells you to.
  • Do not give CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL to anyone else, even if they have the same condition as you.
  • Do not use this medicine in children under 12 years of age.

Driving or using machines

Using this medicine is not known to affect your ability to drive or use machines.

Looking after your medicine

  • Keep your medicine in its original container until it is time to take them.
  • Keep your medicine in a cool dry place where the temperature stays below 25°C.

Store it in a cool dry place away from moisture, heat or sunlight; for example, do not store it:

  • in the bathroom or near a sink, or
  • in the car or on window sills.

Heat and dampness can destroy some medicines.

Keep it where children cannot reach it.

A locked cupboard at least one-and-a-half metres above the ground is a good place to store medicines.

Getting rid of any unwanted medicine

If you no longer need to use this medicine or it is out of date, take it to any pharmacy for safe disposal.

Do not use this medicine after the expiry date.

6. Are there any side effects?

All medicines can have side effects. If you do experience any side effects, most of them are minor and temporary. However, some side effects may need medical attention.

See the information below and, if you need to, ask your doctor or pharmacist if you have any further questions.

Do not be alarmed by the following list of possible side effects. You may not experience any of them.

Common side effects

Common side effectsWhat to do
  • Nausea (feeling sick)
  • vomiting (upset stomach)
  • stomach or bladder irritation (including a burning sensation or pain when urinating)
  • rash
  • diarrhoea (loose bowel)
  • pain round the abdomen
Speak to your doctor or pharmacist if you have any of these common side effects and they worry you.

Tell your doctor or pharmacist if you notice anything else that may be making you feel unwell.

Other side effects not listed above may also occur in some people. If you are hypersensitive to methenamine hippurate, formaldehyde or any of the other ingredients of this medicine (listed at the end of this leaflet), you may experience

  • shortness of breath
  • wheezing or difficulty breathing
  • swelling of the face, lips, tongue or other parts of the body
  • rash, itching or hives on the skin.

Most side effects of CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL are mild and do not last long but if they persist, bother you or are signs of an allergy, talk to your pharmacist or doctor or go to Accident and Emergency at your nearest hospital.

Reporting side effects

After you have received medical advice for any side effects you experience, you can report side effects to the Therapeutic Goods Administration online at www.tga.gov.au/reporting-problems. By reporting side effects, you can help provide more information on the safety of this medicine.

7. Product details

This medicine is available over-the-counter without a doctor's prescription.

What CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL contains

Active ingredient
(main ingredient)		Methenamine hippurate
Other ingredients
(inactive ingredients)		Colloidal anhydrous silica
Povidone
Magnesium stearate

Do not take this medicine if you are allergic to any of these ingredients.

What CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL looks like

CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL tablets are white to off-white, capsule-shaped, biconvex with a ‘H’ and ‘1’ debossed on either side of a scoreline on one side, and plain on the other side.

CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL is available in bottles of 100 tablets.

Who distributes CHEMISTS' OWN URINARY TRACT ANTIBACTERIAL

Arrotex Pharmaceuticals Pty Ltd
15 – 17 Chapel Street
Cremorne VIC 3121
Australia

Australian Registration Number

AUST R 380191

This leaflet was prepared in March 2023.

Published by MIMS June 2024

BRAND INFORMATION

Brand name

Chemists' Own Urinary Tract Antibacterial

Active ingredient

Methenamine hippurate

Schedule

Unscheduled

 

1 Name of Medicine

Methenamine hippurate.

2 Qualitative and Quantitative Composition

Each tablet contains 1 gram of methenamine hippurate.
For the full list of excipients, see Section 6.1 List of Excipients.

3 Pharmaceutical Form

White to off-white, capsule-shaped, biconvex tablets debossed with 'H' and '1' on either side of the scoreline on one side and is plain on the other side.

4 Clinical Particulars

4.1 Therapeutic Indications

Methenamine hippurate tablets are indicated for prophylaxis or suppression of bacteriuria associated with chronic or recurrent infection of the urinary tract.

4.2 Dose and Method of Administration

Adults and children 12 years or older.

One tablet orally twice daily.

Children under 12 years.

Not recommended.

Special populations.

Renal impairment.

No dose adjustments for patients with mild or moderate renal insufficiency.
Methenamine hippurate is not recommended for use by patients with neurogenic bladder, renal tract abnormalities or using long-term catheters (see Section 4.3 Contraindications).

4.3 Contraindications

Hypersensitivity to methenamine hippurate, formaldehyde or to any of the excipients listed, see Section 6.1.
Patients with severe hepatic dysfunction, severe renal failure (eGFR < 10 mL/min/1.73 m2), severe dehydration, metabolic acidosis or gout.

4.4 Special Warnings and Precautions for Use

The underlying causes and risk factors for urinary tract infections should be investigated, and changes to perineal hygiene, sexual practices, urinary voiding and diet to maintain the normal urinary tract flora may be indicated before pharmacological interventions.
The effectivity of methenamine hippurate as a prophylactic agent depends on the acidity of urine, the bacterial species and counts in urine, their susceptibility to methenamine, and the exposure interval to formaldehyde that is hydrolysed from methenamine (see Section 5.1 Pharmacodynamic Properties, Mechanism of action). Methenamine may be ineffective when the urinary tract is colonised by new species, when bacteria multiply quickly under certain conditions, or migrate from the lower urinary tract to the kidneys, therefore patients should be encouraged to consult their doctor at the onset of signs and symptoms of infection.
Bacteriological analysis of a urine sample is recommended to confirm the clinical diagnosis. When antibiotic treatment of bacteriuria or urinary tract infection is indicated, prophylaxis with methenamine hippurate should be stopped until infection is cleared and urine becomes sterile (< 104 counts per mL).

Use in the elderly.

The elderly are at higher risk of urinary tract infections because of changes in oestrogen levels (women), prostate problems (men), incontinence, increased use of medications, surgical or medical interventions including catheters, or decreased mobility and personal hygienic practices. No difference in the safety of methenamine hippurate in the elderly compared to the younger population has been observed.

Paediatric use.

It is not recommended for children under 12 years of age (see Section 4.2).

Effects on laboratory tests.

In laboratory tests using acid hydrolysis of urine during pregnancy, the presence of methenamine or formaldehyde can result in unmeasurably low oestriol results. Enzymatic hydrolysis will provide more accurate results.
Methenamine can affect the determination of steroids, catecholamines and 5-hydroxyindole acetic acid in urine and give false results depending on the analytical method used.

4.5 Interactions with Other Medicines and Other Forms of Interactions

Sulphonamides.

Some sulphonamides may form an insoluble crystalline precipitate with formaldehyde in urine, therefore concurrent administration with methenamine should be avoided.

Alkalising agents.

Methenamine hydrolyses into the therapeutically active formaldehyde under acidic conditions in urine, therefore concomitant use with agents that make urine alkaline or urinary alkalising agents such as potassium citrate or acetazolamide reduce the effectivity of methenamine and should be avoided.

4.6 Fertility, Pregnancy and Lactation

Effects on fertility.

There are no human data available on fertility. Data from studies in rats do not indicate any effects on female fertility, while effects on male fertility have not been adequately tested (see Section 5.3 Preclinical Safety Data).
(Category A)
There is inadequate evidence of safety of methenamine hippurate in human pregnancy, but it has been in wide use for many years without apparent ill consequence. Animal studies are insufficient with respect to reproductive toxicity.
In limited studies in pregnant rabbits with methenamine hippurate at approximately 3 times the clinical dose based on body surface area, there was increased post-implantation loss resulting in lower litter sizes and a limited occurrence of foetal deformities including shortness of tail and malrotation of limbs. No effects on development were noted at doses equivalent to the clinical dose. Methenamine hippurate, administered at approximately 3 times the clinical dose, based on body surface area, did not adversely affect the fertility of female rats. Effects on male fertility have not been adequately studied.
As a precautionary measure, it is preferable to avoid the use of methenamine hippurate during pregnancy.
 Methenamine is excreted in breast milk but the quantities will be insignificant to the infant. Mothers can therefore breast feed their infants.

4.7 Effects on Ability to Drive and Use Machines

None.

4.8 Adverse Effects (Undesirable Effects)

The safety of methenamine hippurate is estimated from its well-established use and published literature on studies involving small numbers of patients. Adverse effects are listed below by system organ class and frequency terms, which defines as: very common (≥ 1/10), common (≥ 1/100 to < 1/10), uncommon (≥ 1/1,000 to < 1/100), rare (≥ 1/10,000 to < 1/1,000), very rare (< 1/10,000) and not known (cannot be estimated from available data).

Gastrointestinal disorders.

Uncommon: gastric irritation, nausea, vomiting.
Not known: diarrhoea, abdominal pain.

Skin and subcutaneous disorders.

Uncommon: rash, pruritus.

Renal and urinary disorders.

Uncommon: irritation of the bladder and dysuria.
Albuminuria and hematuria have been reported with high doses (4 to 8 grams daily for 3 to 4 weeks).

Reporting suspected adverse effects.

Reporting suspected adverse reactions after registration 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 at www.tga.gov.au/reporting-problems.

4.9 Overdose

For information on the management of overdose, contact the Poisons Information Centre on 13 11 26 (Australia).

5 Pharmacological Properties

5.1 Pharmacodynamic Properties

Pharmacotherapeutic group: Anti-infectives for systemic use, other antibacterials. ATC Code: J01XX05.

Mechanism of action.

Methenamine hippurate is a urinary antibacterial agent with a wide spectrum covering both gram-positive and gram-negative organisms. Urinary antibacterial activity can be shown within 30 minutes of administration.
The antibacterial action of methenamine hippurate arises from the slow release of formaldehyde when methenamine is hydrolysed in acidic urine.
Formaldehyde denatures the proteins and nucleic acid of bacteria, in particular E. coli, enterococci and staphylococci. Enterobacter aerogenes is generally resistant while urea splitting bacteria such as Proteus and Pseudomonas species are inhibited by methenamine only when urine is sufficiently acidic.
A formaldehyde concentration above 25 micrograms per mL of urine maintained for about 2 hours is effective as a bactericidal. Higher urinary pH, flow rates and frequency decrease the formation, concentration and exposure time of formaldehyde and therefore its effectivity.

Clinical trials.

The authors of a Cochrane review of methenamine hippurate for prevention of urinary tract infections (Lee et al, 2012) concluded that methenamine hippurate may be effective for preventing UTI in patients without renal tract abnormalities, particularly when used for short term prophylaxis, but that it does not appear to work in patients with neuropathic bladder or in patients who have renal tract abnormalities.
In a randomised, double blind, long term, crossover study (Cronberg et al, 1987) 1 g twice daily of methenamine hippurate was compared with placebo for its preventive effect on recurrent attacks of acute cystitis. Methenamine hippurate and placebo were interchanged every six months for two years. Out of 21 enrolled patients, 14 completed the first year and 13 both years of treatment, which permitted the evaluation of 27 patient years. There were 52 episodes of acute cystitis caused by reinfection: 41 occurred during placebo treatment and only 11 during the methenamine hippurate regimen (p < 0.01).

5.2 Pharmacokinetic Properties

Absorption.

Following oral administration, methenamine is rapidly absorbed from the gastrointestinal tract, with a peak plasma concentration of about 30 mg/L occurring approximately 1-2 hours after ingestion of a single dose, then declines at a mean elimination half-life of about 4 hours.
The peak plasma concentration from twice daily dosing is about 35 mg/L at steady-state, indicating that no drug accumulation takes place.

Distribution.

The average distribution volume was about 0.56 L/kg, which is similar to the total body water in adults.

Metabolism.

A small proportion of methenamine is degraded by stomach acid to formaldehyde, which is absorbed and quickly converted to formic acid - which in turn is oxidised to carbon dioxide and water or eliminated quickly through the kidneys. The remaining methenamine is unchanged until excreted by the kidneys.

Excretion.

Excretion is by both tubular secretion and glomerular filtration. About 82% of a single methenamine dose is recovered intact in urine within 24 hours, while about 88% is recovered from 1 g twice daily dosing after a 12-hour interval.

5.3 Preclinical Safety Data

Genotoxicity.

Limited in vitro tests indicate that methenamine is non-mutagenic to Salmonella typhyimurium strains in the presence of S9, but some mutagenic effects with metabolic activation were observed after nitrosation.

Carcinogenicity.

In limited studies, no evidence of carcinogenic activity was found in mice and rats, and methenamine did not induce neoplasms.

6 Pharmaceutical Particulars

6.1 List of Excipients

The tablet also contains the following inactive ingredients: colloidal anhydrous silica, povidone and magnesium stearate.

6.2 Incompatibilities

See Section 4.5 Interactions with Other Medicines and Other Forms of Interactions.

6.3 Shelf Life

In Australia, information on the shelf life can be found on the public summary of the Australian Register of Therapeutic Goods (ARTG). The expiry date can be found on the packaging.

6.4 Special Precautions for Storage

Store below 25°C.

6.5 Nature and Contents of Container

HDPE bottles with PP screw caps containing 100 tablets, enclosed in a carton.

6.6 Special Precautions for Disposal

In Australia, any unused medicine or waste material should be disposed of by taking to your local pharmacy.

6.7 Physicochemical Properties

Methenamine hippurate is a white to off-white powder. It is freely soluble in water.
Chemical name: 2-benzamidoacetic acid; 1,3,5,7-tetrazatricyclo[3.3.1.13,7]decane.

Chemical structure.


CAS number.

5714-73-8.
Molecular formula: C15H21N5O3. Molecular weight: 319.36.

7 Medicine Schedule (Poisons Standard)

Not scheduled.

Summary Table of Changes