Small molecule
PubChem CID 3957
Loratadine
Claritin
- Mechanism of action
- Second-generation H1 histamine receptor antagonist
- In plain language
- Blocks histamine, the chemical that triggers sneezing and itching during an allergic reaction, but stays mostly out of the brain — so it controls symptoms without much drowsiness.
- How it works
- Loratadine is a long-acting, second-generation tricyclic antihistamine that acts as a selective, competitive antagonist at peripheral histamine H1 receptors, blocking histamine's downstream effects on vascular permeability, smooth-muscle tone, and sensory-nerve stimulation. Because it is a substrate for P-glycoprotein-mediated efflux at the blood-brain barrier, it achieves minimal CNS penetration at therapeutic doses, limiting central H1-receptor occupancy and the sedation typical of first-generation antihistamines. Following oral administration it undergoes extensive first-pass hepatic metabolism to its active metabolite, desloratadine, which retains H1-antagonist activity and extends the drug's effective duration.
- Therapeutic applications
- Indicated for temporary relief of symptoms associated with seasonal and perennial allergic rhinitis, including rhinorrhea, sneezing, and pruritus of the nose or throat, as well as ocular pruritus and lacrimation.
- Class
- Small molecule
- Therapeutic area
- Allergy / Immunology
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