FR183998 free base is an inhibitor of Na+/Ca2+ Exchanger.

Na+, H+ exchange (rat platelet):6.5 nM , Na+, H+ exchange (rat lymphocytes):0.3 nM , Na+, H+ exchange (human platelet):3.1 nM

FR183998 free base has potent inhibitory effects on Na+/H+ exchanger in rat lymphocytes, rat platelets, and human platelets with IC50s of 0.3 nM, 6.5 nM, and 3.1 nM, respectively[1].

Administered intravenously at 1 mg/kg, FR183998 free base diminishes the serum elevation of alanine transaminase, aspartate transaminase, and lactate dehydrogenase caused by hepatic ischemia/reperfusion (I/R), while also preventing hepatic necrosis, apoptosis, and neutrophil infiltration. It inhibits the I/R-triggered activation of NF-κB, downregulates iNOS induction, and curbs nitric oxide production, in addition to reducing the liver's iNOS gene antisense transcript expression in hepatic I/R rats. At dosages of 0.1 and 1.0 mg/kg via intravenous injection, FR183998 free base does not alter hemodynamic parameters, mean blood pressure, or heart rate in conscious rats. Both pre- and post-treatment with FR183998 free base, in doses ranging from 0.01 to 0.10 mg/kg intravenously, dose-dependently mitigates reperfusion-induced ventricular fibrillation and mortality in anesthetized rats, showing ED50 values against ventricular fibrillation of 0.015 mg/kg and 0.070 mg/kg, respectively. Moreover, it significantly reduces myocardial infarct sizes and suppresses arrhythmias in anesthetized rats.