Claritin moa?

Claritin (loratadine) – mechanism of action

• Primary action: It’s a selective peripheral H1‑histamine receptor antagonist.

  • By competitively blocking the H1 receptor on mast cells, endothelial cells, and sensory nerve endings, it prevents histamine from binding and triggering the cascade that causes itching, sneezing, nasal congestion, runny nose, and watery eyes.

• Why it’s “non‑sedating”:

  • Loratadine has very low ability to cross the blood‑brain barrier, so it largely spares central H1 receptors that mediate drowsiness.
  • This is why Claritin is often called a “second‑generation” antihistamine.

• Metabolite contribution:

  • After ingestion, loratadine is metabolized in the liver to the active metabolite desloratadine, which also contributes to the antihistaminic effect.

• Overall effect:

  • By blocking peripheral H1 receptors, Claritin reduces the vascular permeability, smooth‑muscle contraction, and sensory nerve activation that produce allergic symptoms, giving relief without the sedative side effects typical of first‑generation antihistamines.