Zyrtec (Antihistamine)

What is Zyrtec?

Zyrtec is a Pharmacy Only Medicine widely used to relieve the symptoms of seasonal and perennial allergies, as well as chronic hives.

As a second-generation H1-receptor antagonist, it is a carboxylated metabolite of hydroxyzine that causes significantly less drowsiness than first-generation antihistamines because it does not easily cross the blood-brain barrier.

Generic Names:

• Cetirizine Hydrochloride: The primary generic name used globally for this specific antihistamine formulation.

Global Brand Names:

Zyrtec is available under various brand names worldwide.

• Zyrtec (治敏速): The original brand produced by UCB Pharma, widely available in Hong Kong pharmacies.
• Acerox (安敏速): A commonly dispensed generic version found throughout Hong Kong.
• Tirlor (特露): A local registered generic formulation available in Hong Kong.

These names all refer to the same medication. It's important to note that while the active ingredient is the same, different countries may have different regulations and available medication formulations.

What is Zyrtec used for?

Zyrtec is used to relieve:

• Seasonal allergic rhinitis (hay fever) symptoms like sneezing and runny nose
• Perennial allergic rhinitis triggered by dust mites, pet dander, or indoor molds
• Chronic idiopathic urticaria (chronic hives and itching)
• Allergic conjunctivitis (itchy and red eyes)

How do you use Zyrtec?

Availability:

• Film-coated tablets
• Oral solutions
• Oral drops

Dosage Information:

• Infants (6 months to 2 years): 2.5 mg once daily, subject to medical advice.
• Children (2 to 6 years): 2.5 mg twice daily.
• Children (6 to 12 years): 5 mg twice daily or 10 mg once daily.
• Adults and Adolescents (>12 years): 10 mg once daily.
• Elderlies: Standard dosing unless experiencing renal impairment.

Suitability:

• Adults: Yes
• Children and infants over 6 months: Yes
• Elderlies: Yes, with caution regarding kidney function.
• Pregnant or breastfeeding women: Caution required, only if directed by a physician.

Who cannot take Zyrtec?

Allergies and unsuitability:

• Rare, but possible severe allergic reactions like anaphylaxis.

Conditions where the drug should not be used:

• End-stage renal disease
• Severe renal failure (Creatinine Clearance under 10 mL/min)
• Known allergy to cetirizine, hydroxyzine, or piperazine derivatives

Common side effects of Zyrtec include mild drowsiness, fatigue, dry mouth, headache, and sore throat. In children, it may occasionally cause paradoxical central nervous system stimulation, resulting in irritability or insomnia.

Severe adverse reactions are rare but require immediate emergency medical care. These include severe swelling (angioedema), anaphylaxis, blurred vision, or signs of liver dysfunction.

• Avoid alcohol and other central nervous system depressants to reduce the risk of extreme drowsiness and impaired alertness.
• Use with caution if you have a history of urinary retention or enlarged prostate, as antihistamines can worsen the condition.
• Check with a doctor before use if you suffer from epilepsy or are at risk of convulsions.
• Do not exceed the recommended daily dose to minimize the risk of excessive sedation and renal strain.
• Consult a doctor before combining with high doses of Theophylline, as it may decrease the clearance of cetirizine from the body.

Storage information:

• Keep in a cool, dry place below 30°C.
• Keep tablets in their original blister packs to protect them from moisture.
• Store securely out of the reach of children.

Handling instructions:

• Use the measuring device that comes with the oral solution or drops for the correct liquid dose.
• Discard any remaining liquid medication after the expiration timeframe specified on the packaging after opening.

Where is Zyrtec available in Hong Kong?

In Hong Kong, Zyrtec is classified as a Pharmacy Only Medicine. While no prescription is needed, it must be purchased at a registered pharmacy under the direct supervision of a registered pharmacist.

Patients can legally obtain this medication at registered dispensaries displaying the "Rx" logo or at prescription counters within general chain drug stores like Mannings and Watsons.