Loratadine
Loratadine is a second-generation H1 antihistamine used in adults and children for allergic rhinitis and urticaria. It blocks peripheral H1 receptors with very limited central penetration, supporting once-daily dosing with minimal sedation.
- Chemical formula
- C22H23ClN2O2
- CAS number
- 79794-75-5
- ATC code
- R06AX13
- Molecular weight
- 382.88 g/mol
- Drug class
- Second-generation H1 antihistamine
- Also known as
- SCH 29851, Loratadina
What is it?
Loratadine was approved in 1993 and is supplied as oral tablets, orodispersible tablets and oral syrup. It is dispensed both with and without prescription in most markets. Loratadine is widely used for everyday allergy symptoms because it produces minimal sedation at standard doses and is well tolerated. The active metabolite desloratadine is also marketed separately under different brand names.
Mechanism of action
Loratadine selectively blocks peripheral H1 histamine receptors, antagonising the effects of histamine released during allergic reactions. The result is reduced vasodilation, decreased capillary permeability, suppression of pruritus and limitation of urticarial responses. The molecule has very low central nervous system penetration, which explains its minimal sedative profile, and high selectivity over muscarinic and adrenergic receptors limits anticholinergic effects.
Pharmacokinetics
Loratadine is rapidly absorbed orally, with peak plasma concentrations reached after one to two hours. It undergoes extensive hepatic metabolism, mainly by CYP3A4 and CYP2D6, producing the active metabolite desloratadine. Plasma protein binding of loratadine is approximately 97% and of desloratadine 73% to 77%. The combined effective half-life is approximately 28 hours, supporting once-daily dosing. Hepatic impairment and CYP3A4 inhibitors increase exposure.
Indications
Loratadine is approved in adults and children for the treatment of allergic rhinitis, including seasonal and perennial forms, and chronic idiopathic urticaria. According to international guidelines, it is one of the recommended second-generation antihistamines for first-line treatment of these conditions. Loratadine is not the first-line treatment for severe asthma or anaphylaxis. Paediatric dosing is age and weight-based.
Safety profile
Loratadine is generally very well tolerated. Common adverse effects are mild headache, somnolence and gastrointestinal symptoms. Sedation is uncommon at the recommended dose. According to the prescribing information, dose adjustment is required in significant hepatic impairment and may be needed in elderly patients. Drug interactions include potentially increased exposure with strong CYP3A4 inhibitors, but clinical relevance is generally low at standard doses.
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Frequently asked questions
How is loratadine different from cetirizine? ▾
Both are second-generation antihistamines, but loratadine has even less central penetration and produces less sedation than cetirizine on average. Cetirizine may have a faster onset of action and slightly stronger effect on chronic urticaria in some studies. The choice between them is often a matter of individual tolerability and response. According to international guidelines, both are recommended first-line options for allergic rhinitis and chronic urticaria.
Can loratadine be taken every day? ▾
Yes. Loratadine is approved for daily use in chronic allergic rhinitis and chronic urticaria. According to the prescribing information, daily dosing is well tolerated for prolonged periods. Periodic reassessment with the prescriber is still recommended, particularly when symptoms change, other treatments are added or hepatic function changes.
Does loratadine interact with other medications? ▾
Loratadine has limited clinically significant interactions. Strong CYP3A4 inhibitors such as ketoconazole or erythromycin can increase plasma concentrations, but this rarely leads to symptomatic effects at standard doses. Combination with alcohol may produce additive mild sedation in sensitive individuals. According to the prescribing information, patients should disclose all concomitant medications and chronic conditions to the prescriber, especially hepatic disease.
Can children take loratadine? ▾
Yes, in age- and weight-based dosing. Loratadine is approved in children from age two in some markets, with a graduated dose schedule defined in the prescribing information. Liquid formulations facilitate accurate paediatric dosing. According to clinical guidelines, paediatric prescribing should be discussed with a paediatrician or pharmacist, particularly in chronic conditions or in young children with hepatic impairment.
What are the main contraindications for loratadine? ▾
Loratadine is contraindicated in known hypersensitivity to the molecule or its excipients. Caution is required in significant hepatic impairment, where dose adjustment is needed. Use during pregnancy and breastfeeding should be discussed with the prescriber. According to the prescribing information, the medical history must be reviewed by a clinician before any prescription, particularly when other allergy or CNS-active medications are already being taken.
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