Thiazinamium chloride possesses potent anticholinergic and antiallergic activity and inhibits TxB2 synthesis with IC50 value of 0.2 µM.
TxB2 synthesis by resting macrophages is inhibited by thiazinamium chloride and promethazine in a dose-dependent manner. Thiazinamium chloride inhibits TxBz synthesis but had no effect on the ingestion of zymosan particles. In contrast, chlorpromazine inhibits phagocytosis but not TxBz synthesis except at lo-3 M. Under the condition where indomethacin, a nown cyclooxygenase inhibitor, is inhibitory, promethazine but not thiazinamium chloride inhibits TxB2 synthesis from exogenous arachidonic acid. Treatment of macrophages with promethazine and chlorpromazine but not thiazinamium chloride results in a reduction in the oxidative burst during phagocytosis. Furthermore, the ability of thiazinamium chloride to selectively inhibit arachidonic acid metabolism may contribute to its bronchodilator/antiallergic activity[1].
[1]. Chang J, et al. Effects of thiazinamium chloride, promethazine and chlorpromazine on thromboxane B2 synthesis, phagocytosis and respiratory burst by rat alveolar macrophages. Biochem Pharmacol. 1983 Sep 15;32(18):2671-7.