Histamine receptor antagonists nonsedating

Terfenadine was introduced into the marketplace as the first nonsedating histamine-1 (Hj) receptor antagonist. It was launched in the United States in 1985 under the brand name Seldane . Its patent protection was near expiration when the drug was voluntarily withdrawn from the antihistamine market in 1997. 

Loratadine (LOR, trade name Claritin ) is a selective peripheral histamine Hi-receptor antagonist. It is a long-acting and nonsedating tricyclic antihistamine, used for the relief of nasal and noimasal symptoms of seasonal allergies and skin rash. The compound is extensively metabolised in the liver to an active metabohte, descarboethoxyloratadine or desloratadine (DCL). 

Histaminei (Hj) receptors mediate such actions as bron-choconstriction and the contraction of smooth muscles in the gastrointestinal tract. Ebastine is a histamine,-receptor blocker. Terfenadine, astemizole, loratadine, and certirizine are second-generation antihistamine agents that are relatively nonsedating. Other H,-receptor antagonists currently undergoing clinical trials are azelastine, ebastine, and levo-cabastine (see also Figures 34 and 59). 

Loratadine. 4 i8-Chloro-Sf6-dihydro-l lH bettzo [bjcyctoh epta[I, 2 bJpyridi n -11 -y f i den e) t-p f peri di n cca rb-oxylic acid ethyl ester ll-l/V- ethoxycarbonyl)-4-piperidyl-idene]-8-chlorO-6,l l -dihydrO-Sif-benzo cyclohepta-tl 2-6]pyridine Sch-29851 Clantin CLaritin Clarityne Lisino. C HjjClNjOji mol wt 3 2.89. C 69 01%, H 6,05%, Cl 9 26%, N 7-32%, O 8.36%. Nonsedating-type histamine H.-receptor antagonist. Prepn F. J. Vtllani, U.S. pat. 

---