Telfast Side Effects: Complete Safety Guide

Common Side Effects of Telfast

According to the Patient Information Leaflet, the following side effects are considered common (may affect up to 1 in 10 people):

• Headache – the most frequently reported side effect.
• Drowsiness – although Telfast is non‑sedating, a small number of people may feel sleepy.
• Nausea – mild stomach discomfort.
• Dizziness – a sensation of light‑headedness.

Uncommon side effects (may affect up to 1 in 100 people) include tiredness or sleepiness.

These effects are usually mild and transient. If any persist or become troublesome, speak to your doctor or pharmacist.

When Do Side Effects Start?

Most side effects from Telfast, if they occur, typically appear within the first few hours after taking the first dose. This coincides with the absorption phase when fexofenadine reaches peak plasma concentrations (1‑3 hours after ingestion).

For example, headache or nausea may begin within 1‑2 hours of taking the tablet. Drowsiness, if it occurs, also tends to appear early. These early effects often resolve as your body adjusts to the medication.

Rare side effects like allergic reactions can occur at any time, including after several days of use. Always remain vigilant for new or worsening symptoms.

How Long Do Side Effects Last? (Timeline)

The duration of side effects depends on the individual and the specific effect. Fexofenadine has an elimination half‑life of approximately 14 hours, meaning it takes about 2‑3 days for the drug to be completely cleared from the body.

• Mild side effects (headache, nausea, dizziness) usually resolve within 24‑48 hours, often as the body becomes accustomed to the medicine.
• Drowsiness or fatigue may last a few hours to a day. If it persists beyond 48 hours, consult your doctor.
• Allergic reactions require immediate medical attention; they do not resolve on their own and may worsen rapidly.

If you experience side effects that last longer than a few days or are bothersome, seek medical advice.

Contraindications: Who Should Not Take Telfast

Telfast 120 mg should not be used in the following situations:

• Allergy: If you are allergic to fexofenadine hydrochloride or any of the excipients (see section 6 of the PIL).
• Children under 12 years: This strength is not licensed for younger children.
• Severe renal impairment: If you have severe kidney disease (creatinine clearance ≤40 mL/min), a lower dose (30 mg once daily) is required – this strength is not suitable without dose adjustment.
• Pregnancy: Telfast should only be used during pregnancy if clearly needed and prescribed by a doctor.
• Breastfeeding: Not recommended because fexofenadine passes into breast milk.
• Rare hereditary problems: Although the tablets are lactose‑free, if you have any other intolerance, check the full excipient list.

Always inform your doctor or pharmacist about your full medical history before starting Telfast.

Food & Drug Interactions

Food Interactions

• Fruit juices (grapefruit, orange, apple): These juices inhibit intestinal OATP transporters, reducing fexofenadine absorption by up to 30‑40%. Avoid taking Telfast with these juices; water is best.
• Food: Taking Telfast with a high‑fat meal may slightly delay absorption (by about 1 hour) but does not reduce overall exposure. For fastest relief, take before a meal.

Drug Interactions

• Antacids containing aluminium or magnesium: These can lower the amount of fexofenadine absorbed. Leave at least 2 hours between taking Telfast and such antacids.
• Other medicines: Always tell your doctor or pharmacist about any other medications you are taking, including herbal remedies and over‑the‑counter products.

Serious Side Effects (Rare)

Although uncommon, the following serious side effects have been reported (frequency not known):

• Severe allergic reactions: swelling of the face, lips, tongue or throat, difficulty breathing, flushing, chest tightness – seek emergency help immediately.
• Fast or irregular heartbeat (palpitations).
• Skin reactions: rash, itching, hives (urticaria).
• Difficulty sleeping (insomnia), nervousness, or bad dreams.
• Diarrhoea.

If you experience any of these, stop taking Telfast and contact a doctor straight away.

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