Loratadine

How it works

It is a selective peripheral histamine H1-receptor antagonist that blocks histamine-mediated allergic responses while crossing the blood-brain barrier poorly, limiting sedation.

Prescribing in practice

• It is generally well tolerated and only mildly sedating, but advise caution as a minority of patients still experience drowsiness affecting driving or skilled tasks.
• Dose adjustment may be needed in significant hepatic impairment.
• Antihistamines are usually withheld before allergy skin testing as they can suppress the response.

Monitoring

No routine monitoring is required for this generally well-tolerated antihistamine.

Counselling the patient

• It is usually taken once daily and is less likely to cause drowsiness than older antihistamines.
• It can be taken with or without food.
• Tell your clinician if symptoms persist despite treatment.

Evidence & guidelines

Non-sedating antihistamines such as loratadine are recommended first-line in NICE guidance for allergic rhinitis and chronic urticaria.