10 mg PO once daily. Do not exceed 10 mg in 24 hours. Second generation antihistamines such as loratadine are preferred over first generation antihistamines. H 1 antagonists, also called H 1 blockers, are a class of medications that block the action of histamine at the H 1 receptor, helping to relieve allergic reactions. Doctors help recognize, prevent, and treat your allergies: The full adult dose of loratadine in other parts of the world is 20 mg. Cetirizine and loratadine are second-generation antihistamines used to treat seasonal allergies and recurrent hives. Though both medications are quite similar, they do have some important differences. Detailed Loratadine / Pseudoephedrine dosage information for adults and children. Includes dosages for Allergic Rhinitis and Nasal Congestion; plus renal, liver and dialysis adjustments. User Reviews for Loratadine. Also known as: Alavert, Claritin, Claritin Reditab, Clear-Atadine, Dimetapp ND, ohm Allergy Relief, QlearQuil All Day & Night, Tavist ND, Wal-itin Diphenhydramine is a sedating antihistamine which is a kind of antihistamine type drug (common cold or symptom drug). Loratadine, sold under the brand names Claritin and Claritin-D (which contains loratadine plus pseudoephedrine), is an over-the-counter antihistamine medication. Terfenadine is an antihistamine formerly used for the treatment of allergic conditions. It was brought to market by Hoechst Marion Roussel (now Sanofi-Aventis) and was marketed under various brand names, including Seldane in the United States, Triludan in the United Kingdom, and Teldane in Australia. It was superseded by fexofenadine in the. Antihistamines. Description Antihistamines are medications that have some similarities in structure to the histamines that cause allergic reactions.