Loratadine
A widely used non-drowsy antihistamine for allergies, cold symptoms, and sneezing.
What is Loratadine?
Loratadine is a second-generation antihistamine used to treat symptoms of allergic rhinitis and common cold such as sneezing, runny nose, watery eyes, itching of nose and throat, and skin allergies.
It is well known for being non-sedating, meaning it does not usually cause sleepiness, making it suitable for daytime use.
History & Development
Loratadine was developed to overcome the major drawback of first-generation antihistamines, which caused excessive drowsiness. It became popular worldwide after being proven safe for long-term allergy management.
Chemical Structure & Properties
- IUPAC name: Ethyl 4-(8-chloro-5,6-dihydro-11H-benzo[5,6]cyclohepta[1,2-b]pyridin-11-ylidene)-1-piperidinecarboxylate
- Molecular formula: C₂₂H₂₃ClN₂O₂
- Molar mass: 382.88 g/mol
- Functional groups: Piperidine ring, ester, aromatic rings
The chemical structure restricts entry into the brain, which explains why loratadine causes minimal central nervous system depression.
Mechanism of Action
Loratadine selectively blocks histamine H₁ receptors in peripheral tissues. Histamine is released during allergic reactions and is responsible for:
- Sneezing
- Runny nose
- Itching
- Red, watery eyes
By blocking H₁ receptors, loratadine prevents allergy symptoms without significantly affecting alertness.
Pharmacokinetics
- Absorption: Well absorbed orally
- Peak plasma time: 1–2 hours
- Protein binding: ~97%
- Metabolism: Liver (converted to desloratadine)
- Half-life: ~8 hours (active metabolite ~27 hours)
- Excretion: Urine and feces
Medical Uses
- Seasonal allergic rhinitis
- Perennial allergic rhinitis
- Common cold symptoms
- Skin allergies (urticaria)
- Dust and pollen allergy
Dosage Guidelines
Adults & children (≥12 years): 10 mg once daily
Children (2–11 years): 5 mg once daily
⚠️ Do not exceed the recommended dose.
Side Effects
- Headache
- Dry mouth
- Fatigue (rare)
- Mild stomach upset
Serious Risks & Warnings
- Liver impairment (dose adjustment needed)
- Rare allergic reactions
Drug Interactions
- Ketoconazole
- Erythromycin
- Alcohol (minimal interaction)
Loratadine vs Cetirizine
Loratadine causes less drowsiness, while cetirizine may provide slightly stronger symptom control.
Frequently Asked Questions
Is loratadine an antibiotic? – No.
Does it cause sleep? – Very rarely.
Can it be taken daily? – Yes, as prescribed.
Is it safe for long-term use? – Yes, under medical guidance.
⚠️ Educational content only. Not a substitute for professional medical advice.