Loratadine

Lore & Background

Loratadine was developed by Schering-Plough as part of a quest for a nonsedating antihistamine. The U.S. Schering also developed desloratadine, an active metabolite of loratadine. Loratadine is a tricyclic antihistamine that acts as a selective inverse agonist of peripheral histamine H1 receptors. It is well absorbed orally and undergoes rapid first-pass hepatic metabolism via cytochrome P450 enzymes. Its metabolite desloratadine is largely responsible for the antihistaminergic effects. The drug's peak effect occurs after 1–2 hours, with a biological half-life averaging eight hours. Common side effects include sleepiness, dry mouth, and headache. Serious side effects are rare. Loratadine is considered largely free of antimuscarinic effects. It is not recommended in children less than two years old. Use during pregnancy appears safe but has not been well studied.

Reader's Guide

Loratadine is significant as a widely used second-generation antihistamine that provides effective allergy relief with reduced sedation compared to older antihistamines. Its development by Schering-Plough aimed to create a blockbuster nonsedating antihistamine, and it succeeded in becoming a common over-the-counter medication after patent expiration. The marketing of Claritin played a notable role in the history of direct-to-consumer advertising of drugs in the United States, with brand awareness commercials that avoided directly stating the drug's purpose. Loratadine is on the World Health Organization's List of Essential Medicines and is available as a generic medication. Its combination with pseudoephedrine was also commonly prescribed. The drug's availability in many forms and combinations worldwide underscores its importance in allergy management.

Did You Know?

• Loratadine is on the World Health Organization's List of Essential Medicines.
• Loratadine is closely related in structure to tricyclic antidepressants such as imipramine.