Loratadine, sold under the brand name Claritin among others, is a medication used to treat allergies. This includes allergic rhinitis (hay fever) and hives. It is also available in combination with pseudoephedrine, a decongestant, known as loratadine/pseudoephedrine. It is taken orally.Common side effects include sleepiness, dry mouth, and headache. Serious side effects are rare and include allergic reactions, seizures, and liver problems. Use during pregnancy appears to be safe but has not been well studied. It is not recommended in children less than two years old. It is in the second-generation antihistamine family of medication.Loratadine was patented in 1980 and came to market in 1988. It is on the World Health Organizations List of Essential Medicines. Loratadine is available as a generic medication. In the United States, it is available over the counter. In 2019, it was the 66th most commonly prescribed medication in the United States, with more than 11 million prescriptions. Medical uses
Loratadine is indicated for the symptomatic relief of allergy such as hay fever (allergic rhinitis), urticaria (hives), chronic idiopathic urticaria, and other skin allergies. For allergic rhinitis, loratadine is indicated for both nasal and eye symptoms - sneezing, runny nose, and itchy or burning eyes.Similarly to cetirizine, loratadine attenuates the itching associated with Kimuras disease. Forms
The drug is available in many different forms, including tablets, oral suspension, and syrup, and in combination with pseudoephedrine. Also available are quick-dissolving tablets. Contraindications
Patients with severe hepatic (liver) disorders may need to start with a lower dose.
No dose adaptation is necessary for elderly or renally (kidney) impaired patients.Loratadine is usually compatible with breastfeeding (classified category L-2 - probably compatible, by the American Academy of Pediatrics). In the U.S., it is classified as category B in pregnancy, meaning  animal reproduction studies have failed to demonstrate a risk to the fetus, but no adequate and well-controlled studies in pregnant women have been conducted. Adverse effects
As a "non-sedating" antihistamine, loratadine causes less (but still significant, in some cases) sedation and psychomotor retardation than the older antihistamines, because it penetrates the blood/brain barrier less.Other side effects include headache and antimuscarinic effects, such as urinary retention, dry mouth, blurred vision, and gastrointestinal problems. Interactions
Substances that act as inhibitors of the CYP3A4 enzyme such as ketoconazole, erythromycin, cimetidine, and furanocoumarin derivatives (found in grapefruit) lead to increased plasma levels of loratadine — that is, more of the drug was present in the bloodstream than typical for a dose. This had clinically significant effects in controlled trials of 10 mg loratadine treatment Antihistamines should be discontinued 48 hours prior to skin allergy tests, since these drugs may prevent or diminish otherwise-positive reactions to dermal activity indicators. Pharmacology
Pharmacodynamics
Loratadine is a tricyclic antihistamine, which acts as a selective inverse agonist of peripheral histamine H1 receptors. The potency of second generation histamine antagonists is (from strongest to weakest) desloratadine (Ki 0.4 nM) > levocetirizine (Ki 3 nM) > cetirizine (Ki 6 nM) > fexofenadine (Ki 10 nM) > terfenadine > loratadine.