Fexofenadine

A highly popular non-drowsy antihistamine used for allergy-related cold symptoms.

What is Fexofenadine?

Fexofenadine is a second-generation antihistamine used to treat symptoms of allergic rhinitis such as sneezing, runny nose, itchy nose, watery eyes, and itching of the throat.

It is especially famous for being completely non-sedating, making it a preferred choice for students, drivers, and working professionals.

History & Development

Fexofenadine is the active metabolite of terfenadine. It was developed to provide the same anti-allergic benefits as terfenadine but without serious cardiac side effects. Today, it is considered one of the safest antihistamines.

Chemical Structure & Properties

• IUPAC name: (±)-4-[1-hydroxy-4-[4-(hydroxydiphenylmethyl)-1-piperidinyl]butyl]-α,α-dimethylbenzeneacetic acid
• Molecular formula: C₃₂H₃₉NO₄
• Molar mass: 501.65 g/mol
• Functional groups: Carboxylic acid, alcohol, aromatic rings, piperidine

The bulky molecular structure prevents it from crossing the blood-brain barrier, which explains the absence of drowsiness.

Mechanism of Action

Fexofenadine selectively blocks histamine H₁ receptors in peripheral tissues. Histamine release during allergy causes:

• Sneezing
• Runny nose
• Itching
• Watery eyes

By blocking these receptors, fexofenadine prevents allergic symptoms without affecting alertness or concentration.

Pharmacokinetics

• Absorption: Moderate oral absorption
• Peak plasma time: 2–3 hours
• Protein binding: ~60–70%
• Metabolism: Minimal (mostly unchanged)
• Half-life: ~14 hours
• Excretion: Feces and urine

Medical Uses

• Seasonal allergic rhinitis
• Perennial allergic rhinitis
• Cold and allergy-related sneezing
• Chronic urticaria (hives)
• Dust and pollen allergy

Dosage Guidelines

Adults: 120 mg once daily (or 60 mg twice daily)

Children (6+ years): 30–60 mg daily

⚠️ Avoid taking with fruit juices (apple, orange, grapefruit).

Side Effects

• Headache
• Dizziness (rare)
• Nausea
• Fatigue (very rare)

Serious Risks & Warnings

• Kidney disease (dose adjustment required)
• No known cardiac toxicity at normal doses

Drug Interactions

• Antacids containing aluminum or magnesium
• Fruit juices (reduce absorption)
• Minimal interaction with alcohol

Fexofenadine vs Loratadine

Fexofenadine is completely non-sedating, while loratadine may cause mild fatigue in some people.

Frequently Asked Questions

Is fexofenadine an antibiotic? – No.

Does it cause sleep? – No.

Can it be taken daily? – Yes.

Is it safe for drivers? – Yes.

⚠️ Educational content only. Not a substitute for professional medical advice.