Loratadine

Histamine H1 receptor antagonist (second-generation), Antihistamine

Loratadine

Claritin, Alavert, Tavist ND

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Summary

Classes

Histamine H1 receptor antagonist (second-generation), Antihistamine

Common uses

Allergic rhinitis▲0▼, Chronic idiopathic urticaria▲0▼

Pharmacy

Starting dose

10 mg PO once daily

Preparations

10 mg tablets; 5 mg ODT and chewables; 1 mg/mL oral syrup; combo Claritin-D (with pseudoephedrine, behind-counter)

US FDA Max

10 mg/d (adults)

Pharmacology

Routes

Oral

Onset

1-3 hours (slower onset than cetirizine; symptom relief somewhat less)

Duration

24 hours

Half-life

~8 hours (parent); ~28 hours (desloratadine, the active metabolite, marketed separately as Clarinex)

Bioavailability

High (oral; food prolongs absorption modestly)

Pregnancy

Generally considered safe; widely used. Loratadine and cetirizine are the most-recommended 2nd-gen H1s in pregnancy and lactation.^{[citation needed]}

Legal status

OTC in US

Purported mechanism

Loratadine is a selective peripheral H1 receptor antagonist with very limited blood-brain barrier penetration, producing antihistaminic effect without significant sedation; it is metabolized by CYP3A4 and CYP2D6 to desloratadine, the longer-half-life active metabolite.▲0▼ Less reliably anticholinergic than first-generation H1s; minimal antiemetic effect. Desloratadine (Clarinex) is the active enantiomer-of-metabolite version marketed as a Rx alternative.