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Cetirizine (Cetirizine HCl)

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

Last Modified: 10 Apr 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

  • Dosage Adherence: Stick to the prescribed dosage and schedule to manage your condition effectively and minimise the risk of side effects. 
  • Awareness of Side Effects: Monitor for signs of stomach ulcers or bleeding, such as bloody stools or coughing up blood, and seek immediate medical attention if they occur. 
  • Drug Interactions: List all your medications and share them with your healthcare provider to avoid potential interactions. 
  • Preventive Measures: To reduce the risk of stomach upset or ulcers, take celecoxib with food or milk. An antacid (e.g. Gaviscon, Maalox), H2-antagonist (e.g. famotidine, ranitidine) or proton pump inhibitor (PPI) (e.g. omeprazole, pantoprazole) may be paired. 
  • Regular Monitoring: Regularly review your treatment with your healthcare provider, especially if you have a history of heart disease or stroke. 
  • Safe Storage: Store celecoxib at room temperature, away from moisture and heat. Keep the medication out of reach of children and pets. 
  • Proper Disposal: Do not keep leftover or expired medication. Find out about take-back programs or consult your pharmacist for disposal instructions.


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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