Quinotolast sodium in the concentration range of 1-100 μg/mL inhibits histamine, LTC₄ and PGD₂ release in a concentration-dependent manner. IC50 & Target: histamine^[1]
leukotriene^[1] In Vitro: Quinotolast inhibits the release of histamine and the generation of leukotriene (LT) C₄ and prostaglandin (PG) D₂ from dispersed human lung cells. Quinotolast (100 μg/mL) significantly inhibits PGD₂ and LTC₄ release. Quinotolast inhibits PGD₂ release by 100% and LTC₄ release by 54%. The inhibitory effect of Quinotolast on histamine release from dispersed lung cells is largely independent of the preincubation period, no tachyphylaxis being observed. Quinotolast shows a significant inhibition of inflammatory mediators from human dispersed lung cells^[1]. Quinotolast also shows strong inhibitory effects on histamine and peptide leukotrienes release from guinea pig lung fragments or mouse cultured mast cells. Quinotolast concentration-dependently inhibits pLTs release from cultured mast cells. The IC₅₀ value for Quinotolast is 0.72 μg/mL^[2]. In Vivo: Quinotolast potently inhibits such type I allergic reactions as passive cutaneous anaphylaxis (PCA) and anaphylactic bronchoconstriction in rats by both intravenous and oral dosing. When Quinotolast is given i.v. to rats, Quinotolast, dose-dependently inhibits PCA. The doses of Quinotolast required to inhibit the reaction by 50% (ED₅₀) is 0.0063 mg/kg. Given p.o., Quinotolast inhibits the reaction. ED₅₀ value for Quinotolast is 0.0081 mg/kg. Although almost complete inhibition is observed with Quinotolast at a dose of 0.32 mg/kg, its effect is slightly attenuated at a dose of 1 mg/kg^[2].