Telfast
A medicine used to treat mild to moderate allergy symptoms, including hay fever and chronic hives, with a low risk of drowsiness.
Last Updated: 10 Sep 2026
What is Telfast?
Telfast is a Pharmacy Only Medicine in Hong Kong widely used to relieve symptoms associated with seasonal allergic rhinitis (hay fever) and chronic idiopathic urticaria (hives).
As a second-generation antihistamine derived from terfenadine, it selectively blocks peripheral H1-receptors without readily crossing the blood-brain barrier, making it significantly less likely to cause drowsiness compared to older first-generation alternatives.
| Medicine Name | Telfast |
| Also Known As | Fexofenadine, Fexofenadine Hydrochloride |
| What It Does | Relieves sneezing, runny nose, itchy eyes, and hives. |
| Active Ingredient | Fexofenadine Hydrochloride |
| How It Works | Blocks histamine from binding to H1-receptors to prevent allergic responses. |
| How to Take It | Taken orally. |
| Forms Available | Tablets, oral suspensions. |
| Typical Dosage | Adults: 120 mg to 180 mg once daily. Paediatric doses calculated by age. |
| Suitable For | Adults, the elderly, and children over 6 years old. |
| Not Suitable For | People allergic to fexofenadine and infants under 6 years old. |
Generic Names:
- Fexofenadine Hydrochloride: The standard generic name used globally for this active ingredient.
Global Brand Names:
Several pharmaceutical companies manufacture fexofenadine under various brand names globally.
- Telfast (退敏快): The primary brand name available in Hong Kong, sold in tablet and pediatric suspension forms.
- Allegra: A prominent international brand name for fexofenadine, sometimes found in Hong Kong via parallel import.
- Fexo: A generic alternative readily available in registered Hong Kong pharmacies.
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 Telfast used for?
Telfast is used to relieve:
- Sneezing and runny nose (rhinorrhea)
- Itchy nose, palate, and throat
- Itchy, watery, and red eyes
- Itching and wheals associated with chronic hives
How do you use Telfast?
Availability:
- Tablets
- Oral suspension
Dosage Information:
- Adults and Children 12 years and older: 120 mg to 180 mg once daily, depending on the condition.
- Children (6 to 11 years): 30 mg twice daily, often administered via pediatric suspension.
- Elderly and Renal Impairment: Lower starting doses, such as 60 mg once daily, may be required.
Suitability:
- Adults: Yes.
- Children: Yes, but only for those over 6 years old with adjusted dosages.
- Elderly: Yes, with caution regarding reduced kidney function.
- Pregnant or breastfeeding women: No, unless deemed strictly necessary by a healthcare provider.
Who cannot take Telfast?
Allergies and unsuitability:
- Rare, but possible allergic reactions.
Conditions where the drug should not be used:
- Known allergy to fexofenadine.
Telfast is generally well-tolerated, but some individuals may experience mild side effects. The most common adverse reactions include headache, dizziness, nausea, and a dry mouth. Although it is a non-drowsy antihistamine, a very small percentage of users may still experience mild drowsiness.
Severe side effects are extremely rare. However, severe hypersensitivity reactions such as angioedema, chest tightness, flushing, and difficulty breathing require immediate medical attention. Overuse or exceeding the recommended daily limit does not provide extra symptom relief and increases the risk of unwanted side effects.
- Do not take with fruit juices (such as orange, apple, or grapefruit) to avoid significantly reducing the drug's absorption and effectiveness.
- Wait at least two hours before or after taking aluminum or magnesium-based antacids to prevent them from interfering with fexofenadine absorption.
- Do not exceed the recommended daily dosage to avoid an increased risk of adverse effects.
- Consult a doctor before use if you have a history of kidney disease or impaired renal function.
- Check with a healthcare provider if you are currently taking erythromycin or ketoconazole, as these may alter plasma levels.
Storage information:
- Keep at room temperature, below 30°C.
- Store in a cool, dry place away from direct sunlight.
- Keep out of sight and reach of children.
Handling instructions:
- Swallow tablets whole with a plain glass of water.
- Use the measuring device that comes with the pediatric oral suspension for the correct dose.
- Do not consume fruit juices within two hours of administering the dose.
Where is Telfast available in Hong Kong?
Telfast and its generic equivalents are classified as a "Pharmacy Only Medicine" in Hong Kong. This means that while no prescription is needed, it must be purchased at a registered pharmacy under the direct supervision of a registered pharmacist.
You can legally obtain this medication at registered dispensaries displaying the "Rx" logo, as well as general chain drug stores like Mannings and Watsons that have a registered pharmacist on duty.
How fast does Telfast work?
Telfast typically begins working to relieve allergy symptoms within one hour of oral intake. The effects usually last for 12 to 24 hours depending on the dosage.
Can I take Telfast with fruit juice?
No, you should not take this medication with fruit juice. Orange, apple, and grapefruit juices can reduce the absorption of fexofenadine by up to 40%, making it less effective.
Will Telfast make me sleepy?
No, Telfast is a non-drowsy antihistamine designed not to cross the blood-brain barrier. However, individual responses vary, and a very small number of people may still experience mild drowsiness.
Is Telfast safe during pregnancy?
No, it is generally avoided during pregnancy unless the benefits strongly outweigh the risks. Always check with a healthcare provider before using antihistamines if you are pregnant or breastfeeding.
Should I take Telfast with or without food?
You can take Telfast with or without food. However, it must be swallowed with plain water and kept away from fruit juices or antacids.
