Also called methenamine hippurate

Hiprex is used to prevent ongoing or recurrent urinary tract infections (UTIs). Find out how to take it safely and possible side effects.

What is Hiprex?

Hiprex is used to prevent ongoing or recurrent urinary tract infections (UTIs). It works by causing your pee (urine) to be acidic and in this way discourages the growth of bugs. It is not effective for the treatment of UTIs but may be considered for preventing UTIs in women. Read more about UTIs in women. 


  • In Aotearoa New Zealand, Hiprex is available as tablets (1 gram).
  • The dose of Hiprex is 1 tablet 2 times a day – every 12 hours is best.
  • If you have a catheter your doctor may increase your dose to 1 tablet 3 times a day.
  • You can buy Hiprex from a Pharmacy or other retail outlets like some supermarkets.

How to take Hiprex

  • Timing: It is best to take Hiprex with food such as with breakfast and dinner. Take each dose with a full glass of water. Take Hiprex regularly to prevent UTIs. Do not wait for symptoms.
  • Swallowing problems: If you find it difficult to swallow the Hiprex tablets, you can crush them and take them with a drink of milk or fruit juice. 
  • Vitamin C: Your doctor may suggest to take vitamin C which can make your urine acidic. Hiprex works best when your urine is acidic.
  • Missed dose: If you forget to take your dose, do not take a double dose to make up for a missed dose. Simply take your next dose as planned.

Interactions with other medicines

  • Do not take Hiprex while you are taking sulfonamide antibiotics such as co-trimoxazole. This increases your risk of kidney stones. 
  • Do not use antacids or urinary alkalinizers (such as sodium bicarbonate  or potassium citrate) while you are taking Hiprex. These cause your pee to be alkaline (opposite to acidic) which makes Hiprex ineffective. 

Precautions before taking Hiprex

  • Do you have gout?
  • Do you have problems with your kidney or liver?
  • Are you pregnant?

If so, it’s important that you tell your doctor or pharmacist before you start Hiprex. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.

What are the side effects of hiprex?

Side effects include skin rash, itching, stomach irritation, nausea (feeling sick) and vomiting (being sick). Some people may experience bladder irritation such as a burning sensation and pain on peeing.

Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product


  1. Methenamine hippurate NZ Formulary
  2. Hiprex 1g tablets EMC PIL Hiprex
Credits: Sandra Ponen, Pharmacist. Reviewed By: Maya Patel, Pharmacist, Auckland Last reviewed: 07 Sep 2021