Sounds like 'seh-TEER-ah-zeen'

Key points about cetirizine

  • Cetirizine is an antihistamine used to treat and prevent allergies such as hay fever.
  • Cetirizine belongs to a group of medicines known as antihistamine.
  • It is also called Zista®, Histaclear®, Zyrtec®, Razene® or Zetop®.
  • Find out how to take it safely and possible side effects.
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Cetirizine is used to treat and prevent allergies such as hay fever (sneezing, runny or itchy nose, itchy eyes) or skin allergies such as hives (itching, redness, lumps). It works by blocking a chemical in your body, called histamine, which is released during an allergic reaction. 

Cetirizine belongs to a group of medicines known as antihistamines. Cetirizine is a non-sedating antihistamine, which means that it is less likely to cause drowsiness or make you feel sleepy. In New Zealand, cetirizine is available as tablets or as a liquid. Read more about antihistamines.

  • The usual dose of cetirizine for adults and children over 12 years, is 1 tablet (10 milligrams) once a day.
  • The dose for children under 12 years will depend on their age and weight. Your doctor or pharmacist will advise you on the correct dose for your child.
  • You can just take cetirizine on the days you need it. It can be restarted if the symptoms come back. 
  • Some people take cetirizine for a few weeks when their allergies are a problem, such as in springtime. Others take it long-term to help control allergy symptoms. 

  • Timing: Take cetirizine once a day at the same time each day. You can take cetirizine with or without food. Swallow the tablet whole, with a glass of water.
  • Missed dose: It is not harmful if you miss your cetirizine dose. If you forget to take your dose, and you usually take it regularly, take it as soon as you remember that day. If it is less than 12 hours for your next dose, just take the next dose at the right time. Do not take double the dose.

  • Are you are pregnant, trying for a baby or breastfeeding?
  • Do you have epilepsy?
  • Do you have any problems with the way your kidneys work?
  • Are you taking or using any other medicines? This includes any medicines that you can buy without a prescription, as well as herbal and complementary medicines.

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

Like all medicines, cetirizine can cause side effects, although not everyone gets them. Often side effects improve as your body adjusts to the new medicine.

Side effects What should I do?
  • Tiredness
  • Sleepiness
  • Try taking cetirizine at night.
  • Be careful when driving or using tools until you know how this medicine affects you.
  • Limit drinking alcohol – it makes these symptoms worse.
  • Changes in eyesight
  • Dry mouth
  • Blurred vision
  • Feeling dizzy or confused
  • Problems passing urine
  • Constipation
  • Headache
  • Tell your doctor.
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(external link)

Here are some things to know when you're taking cetirizine. Other things may be important as well, so ask your healthcare provider what you should know about.

  • Other medicines: Cetirizine may interact with some medicines so check with your pharmacist before starting cetirizine or before starting any new medicines. If taken with other antihistamines (such as some cough and cold medication) it may cause added sleepiness.
  • Driving: Be careful when driving or using tools until you know how this medicine affects you.
  • Limit drinking alcohol while you are taking cetirizine. It may increase your chance of side effects such as sleepiness.  

Razene(external link) Medsafe, NZ
Cetirizine(external link) New Zealand Formulary


5 questions to ask about your medications(external link) Health Quality and Safety Commission, NZ, 2019 English(external link), te reo Māori(external link)'


  1. Cetirizine hydrochloride(external link) New Zealand Formulary
  2. Antihistamines(external link) New Zealand Formulary

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Credits: Sandra Ponen, Pharmacist, Healthify He Puna Waiora. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Angela Lambie, Pharmacist, Auckland

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