Loratadine is a commonly used anti-allergy drug, which belongs to the second generation of long-acting tricyclic antihistamines. It acts quickly, has strong effect, does not contain hormones, and is metabolized into more active desloratadine after absorption by the human body. It competitively inhibits histamine H1 receptor and inhibits allergic symptoms caused by histamine, without obvious anticholine and central inhibitory effects. It is used clinically to relieve symptoms associated with allergic rhinitis, such as sneezing, runny nose and itchy nose, as well as itching and burning of the eyes. It is also used to relieve the symptoms of chronic urticaria and other allergic skin diseases. Toxicology: No mutagenicity or malformation in animal tests. Common adverse reactions include headache, Chemicalbook sleep, fatigue, dry mouth, blurred vision, decreased or increased blood pressure, palpitations, syncope, hyperkinetic activity, changes in liver function, jaundice, hepatitis, liver necrosis, hair loss, seizures, breast enlargement, erythema multiforme, and systemic anaphylaxis. Drug interaction: Drugs that inhibit the function of liver drug metabolizing enzymes can slow down the metabolism of this product, such as itraconazole and ketoconazole. Taking 400mg ketoconazole daily can increase the plasma concentration of this product and its active metabolite decarboxethylloratadine, but no electrocardiogram changes were observed. Combined with macrolide antibiotics, cimetidine, theophylline and other drugs can also inhibit the metabolism of loratadine.