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Cetirizine (Cetirizine HCl)

Cetirizine is an antihistamine that alleviates allergy symptoms by blocking histamine action.

Last Modified: 21 May 2024

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What is Cetirizine?

Cetirizine is an antihistamine that alleviates allergy symptoms by blocking histamine action. 

Active ingredient: Cetirizine Hydrochloride

Global Name

Generic name: Cetirizine 
Brand names: Zyrtec, Aller-Tec, Cetiri-D


What is Cetirizine used for?

Cetirizine treats: 

  • Seasonal allergic rhinitis 
  • Perennial allergic rhinitis 
  • Chronic urticaria (hives) 
  • Acute allergic/hypersensitivity reactions (e.g. to food, food additives, latex rubber)  

How do you use Cetirizine?


Cetirizine is available as tablets, chewable tablets, and syrup. 

Dosage Information:

  • Adults and children 6 years and older: 5 mg to 10 mg once daily, depending on the severity of symptoms. 
  • Children 2 to 6 years: 2.5 mg once or twice daily (syrup). 

Suitable for:

  • Children: Yes, for those 2 years and older.
  • Adults: Yes, widely used.
  • Elderlies: Yes, but with caution if there are kidney issues.
  • Pregnancy: Please consult a healthcare provider. 
  • Lactation: Caution is advised as cetirizine passes into breast milk. 

Not Suitable for:

  • Severe kidney impairment
  • Hypersensitivity to the drug
Cetirizine can generally be taken with or without food.  

Allergies and Warnings:

Cetirizine may interact with alcohol and other CNS depressants, enhancing sedative effects. It should be used with caution in patients with predisposing factors for urinary retention. 

Side Effects

Common side effects include drowsiness, fatigue, and dry mouth. Seek medical attention for severe allergic reactions. 

Pharmacist Tips

  • Accurate Dosing: Use the measuring device that comes with the syrup for accurate dosing, especially in children. 
  • Caution with Activities: Be cautious when driving or operating machinery until you know how cetirizine affects you, as it can cause drowsiness in some individuals. 
  • Avoid Alcohol: Minimise or avoid alcohol consumption while taking cetirizine to prevent increased drowsiness. 
  • Allergy Management: Keep track of your symptoms to help your healthcare provider adjust your dose if necessary. 
  • Safe Storage: Store cetirizine at room temperature, away from light and moisture, and out of reach of children and pets. 
  • Handling Instructions: If using chewable tablets, make sure your hands are dry before handling the medication. 


Where is Cetirizine available in Hong Kong?

Cetirizine is an over-the-counter (OTC) medication that can be sold without a prescription. It is found in all chain drug stores, including Mannings and Watsons.


Is Cetirizine available for purchase over-the-counter?

Yes, Cetirizine is available over-the-counter and as a prescription, depending on the strength.

Can I take Cetirizine with food or should it be on an empty stomach?

Cetirizine can be taken with or without food.

Is it safe to take Cetirizine every day?

Yes, Cetirizine can be taken daily for continuous allergy symptom relief but consult your healthcare provider for long-term use. 

How fast does Cetirizine work? 

Cetirizine can take effect within 20 minutes to 1 hour of intake in patients with normal kidney function.

How long does Cetirizine stay in your system?  

Cetirizine has a half-life of approximately 8 hours and is usually eliminated from the system around 48 hours after the last dose.  


This website provides content related to drug use and medicine for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Do not use the information on this website to diagnose or treat a health problem or disease without consulting a qualified healthcare provider. The website's owners and contributors are not liable for any repercussions, adverse effects, or consequences resulting from the use of any medication or information provided herein.

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