Loratadine

Products

Loratadine is commercially available in tablet form (Claritine, Claritine Pollen, generics). It has been approved in many countries since 1991. The active metabolite desloratadine is also available (Aerius, generics).

Structure and properties

Loratadine (C₂₂H₂₃ClN₂O₂, M_r = 382.9 g/mol) exists as a white crystalline powder that is practically insoluble in water. It is a prodrug and is biotransformed to desloratadine (descarboethoxyloratadine) and other metabolites. Loratadine is structurally related to other antihistamines such as cyproheptadine and to tricyclic antidepressants.

Effects

Loratadine (ATC R06AX13) has antihistamine and antiallergic properties and is less sedating than 1st-generation antihistamines. It is not anticholinergic or cardiotoxic like astemizole or terfenadine. The effects are due to selective antagonism at histamine H1 receptors.

Indications

Hay fever
Allergic rhinitis
Hives (Urticaria)
Allergic conjunctivitis

Dosage

According to the package insert. Because loratadine and its active metabolite have a long half-life, once-daily administration is sufficient. The effect is more rapid if taken fasting.

Contraindications

Hypersensitivity

For complete precautions, see the drug label.

Interactions

Loratadine is biotransformed by CYP3A4 and CYP2D6. Corresponding drug-drug interactions are possible. The effects of alcohol are not enhanced, according to the SmPC.

Adverse effects

The most common possible adverse effects include:

Diarrhea, dry mouth, dyspepsia, increase in appetite, pharyngitis.
Cough, nosebleeds, rhinitis, upper respiratory tract infections.
Fatigue
Dizziness, lightheadedness, nausea