Control of venom-induced tissue injury in copperhead snakebite patients: a post hoc sub-group analysis of a clinical trial comparing F(ab')(2) to Fab antivenom

Introduction Fab antivenom (FabAV) halts progression of tissue injury and improves recovery in copperhead snakebite. It is unknown if F(ab')(2)AV does as well. The objective of this study was to compare control of tissue injury in copperhead snakebite patients treated with F(ab')(2)AV versus FabAV. Methods We performed a post hoc analysis of copperhead envenomated patients in a clinical trial comparing F(ab')(2)AV to FabAV. The outcomes for this analysis are the number of repeat doses required to obtain initial control, the number of patients requiring unscheduled doses during maintenance, and the time from antivenom administration to initial control. Results Twenty-one (13 F(ab')(2)AV, 8 FabAV) were copperhead patients. Median age was 46 years with a male predominance. Baseline severity was similar. One (8%) F(ab')(2)AV and 2(25%) FabAV patients required repeat initial dosing, difference = 17%, (95%CI -18, 57%). One (8%) F(ab')(2)AV and 1(13%) FabAV patients required additional doses after maintenance, difference = 5%, (95%CI -27, 45%). Median time to initial control was 2.7 range (2.0, 9.3) hours and 3.5 range (2.0, 7.4) for F(ab')(2)AV and FabAV respectively, difference -0.8 h (95% CI -2.6, 0.9). Conclusions This exploratory analysis suggests that the available measures of the control of venom-induced tissue injury are similar between antivenom subgroups.

Automated summary

This study compared the control of tissue injury in copperhead snakebite patients treated with F(ab')2AV versus FabAV and found that the outcomes were similar between the two antivenom subgroups, indicating no significant difference in their effectiveness in controlling venom-induced tissue injury.