Anti-allergic, antihistamine/H₁-antagonist: 1-Alkoxyalkyl-2-alkylthiobenzimidazoles as Highly Potent Antihistamines

Summary

Novelty: A new class of alkylthiobenzimidazole derivatives showing antihistaminic and anti-allergic activities is disclosed.

Biology: The compounds inhibit histamine induced mortality in guinea pigs; (ID₅₀ = 10.9 μg/kg ip compared to 735 μg/kg ip for terfenadine) and showed H₁ receptor binding (IC₅₀ = 2.4 nM, compared to 283.1 nM for terfenadine). The anti-allergic activity of the compounds is evaluated in male rats by studying protection against mortality induced by compound 48/80 (ID₅₀ = 8 μg/kg compared to 1990 μg/kg for terfenadine).

Chemistry: 1-(2-Ethoxyethyl)-2-(2-dimethylaminoethylthio)-benzimidazole is one of two specifically claimed compounds.