FR183998 free base is a potent Na + /H + -exchange inhibitor, with IC 50 s of 0.3 nM, 3.1 nM and 6.5 nM by measurement of pH i change in rat lymphocytes, rat and human platelets, respectively. In Vitro FR183998 free base is a Na + /H + -exchange inhibitor, with IC 50 s of 0.3 nM, 6.5 nM and 3.1 nM by measurement of pH i change in rat lymphocytes, rat and human platelets, respectively. MCE has not independently confirmed the accuracy of these methods. They are for reference only. In Vivo FR183998 (0.1 and 1.0 mg/kg, i.v.) shows no effect hemodynamic parameters, and does not affect mean blood pressure and heart rate in conscious rats. Pretreatment of 0.01, 0.032, 0.10 mg/kg FR183998 or posttreament of 0.032 and 0.10 mg/kg FR183998 via intravenous administration, dose-dependently reuces reperfusion-induced ventricular fibrillation (VF) and mortality in reperfusion-induced arrhythmias in anesthetized rats, with ED 50 s against VF of 0.015 mg/kg and 0.070 mg/kg, respectively. FR183998 also reduces myocardial infarct sizes, and suppresses the arrhythmias in anesthetized rats . FR183998 (1 mg/kg, i.v.) reduces the increase in serum levels of alanine transaminase, aspartate transaminase, and lactate dehydrogenase induced by hepatic I/R, and prevents the incidences of hepatic necrosis, apoptosis, and neutrophil infiltration. FR183998 blocks the I/R-induced activation of the NF-κB, reduces induction of iNOS and inhibits the production of nitric oxide. FR183998 also decreases the expression of the iNOS gene antisense transcript in the liver of hepatic I/R rats. MCE has not independently confirmed the accuracy of these methods. They are for reference only. Form:Solid IC50& Target:IC50: 0.3 nM (Na + /H + -exchange, Rat lymphocytes), 3.1 nM (Na + /H + -exchange, Human platelet), 6.5 nM (Na + /H + -exchange, Rat platelet)