Mepyramine, also known as pyrilamine, is a first generation antihistamine, targeting the H₁ receptor as an inverse agonist. Mepyramine rapidly permeates the brain, often causing drowsiness. It is often sold as a maleate salt, pyrilamine maleate.

The medication has negligible anticholinergic activity, with 130,000-fold selectivity for the histamine H₁ receptor over the muscarinic acetylcholine receptors (for comparison, diphenhydramine had 20-fold selectivity for the H₁ receptor).