Heat and motion stability of polyvalent Crotalidae antivenin, ovine Fab

This study was conducted to test the hypothesis that a Fab-based crotalid antivenin (FabAV) in commercially packaged vials will remain effective under more extreme heat and motion conditions than would be expected in field settings. Vials containing FabAV were subjected to heat or motion. The effect of heat or motion on the ED50 of FabAV was determined using a mouse model of crotalid snake envenomation. The ED50 for the heat stability groups (expressed as a ratio of mg antivenin to mg venom) were as follows: 4 degrees C x 60 days (control) = 26.5, 70 degrees C x 60 days = 66.3, 70 degrees C x 30 days = 52.4, 50 degrees C x 60 days = 25.8, 50 degrees C x 30 days = 34.0. The ED50 for the two motion stability groups were similar: 4 degrees C x 60 days = 40.3 and 70 degrees C x 60 days = 48.3. These results indicate that FabAV is heat stable at 50 degrees C for 60 days, but had less potency when heated to 70 degrees C for 30 days. FabAV appears less potent after agitation, but remains effective in the mouse model. We conclude that FabAV can be safely stored for at least 60 days without refrigeration under most field conditions where snake envenomation may occur.