Nafamostat mesilate, a kallikrein inhibitor, prevents pain on injection with propofol

We have examined the preventative effect of nafamostat mesilate, a kallikre in inhibitor, on pain on injection with propofol in a randomized, double-bl ind study. A control group (n=110) and a nafamostat (n=103) group received 5% glucose 0.02 mi kg(-1) and nafamostat 0.02 mg kg(-1) diluted with 5% glu cose, respectively, followed 1 min later by 1% propofol injected at a rate of 200 mg min(-1) Pain scores recorded during injection of propofol were si gnificantly less in the nafamostat than in the control group. In another 10 patients, blood concentrations of nafamostat were measured after administr ation of nafamostat 0.02 mg kg(-1) i.v. Mean nafamostat: concentration 1 mi n after injection was 0.1 (SD 0.05) mu mol litre(-1), which is sufficient t o inhibit plasma kallikrein activity. We conclude that pretreatment with na famostat 0.02 mg kg(-1) significantly reduced pain on propofol injection an d this effect may be caused by a reduction in kallikrein activity.