Quinotolast inhibits the release of histamine and the generation of leukotriene (LT) C ₄ and prostaglandin (PG) D ₂ from dispersed human lung cells. Quinotolast (100 μg/mL) significantly inhibits PGD ₂ and LTC ₄ release. Quinotolast inhibits PGD ₂ release by 100% and LTC ₄ 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. 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 IC ₅₀ value for Quinotolast is 0.72 μg/mL.

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% (ED ₅₀ ) is 0.0063 mg/kg. Given p.o., Quinotolast inhibits the reaction. ED ₅₀ 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.