Comparison of the Doses Needed to Achieve Initial Control for F(ab')₂ vs. Fab Antivenom in North American Pit Viper...

There are only two antivenoms on the market approved for North American pit viper envenomations; crotalidae polyvalent immune Fab (ovine) and crotalidae immune F(ab')₂ (equine). There is currently no consensus on which agent may be more effective.

This study aimed to investigate the efficacy and safety of F(ab')₂ compared with Fab regarding systemic and local effects of North American pit viper envenomation.

Patients two years of age and older were retrospectively included and separated into groups if they received Fab or F(ab')₂. The primary outcome compared the amount of Fab or F(ab')₂ doses needed to achieve initial control. Secondary outcomes included incidence of recurrent coagulopathies, skin and soft tissue injury, 30-day readmission, length of stay, cost of drug therapy, and adverse events. Statistical significance was set at p < 0.05.

114 patients were included, 57 in each group. F(ab')₂ patients required less doses to achieve initial control (1 vs. 4 doses; p < 0.01) and had a shorter length of stay (36 vs. 46 hours, p < 0.01). There were no differences in recurrent coagulopathies [20 (F(ab')₂) vs. 13 (Fab)], serious adverse events [1 (F(ab')₂) vs. 0 (Fab)] and readmission within 30 days [1 (F(ab')₂) vs. 0 (Fab)]. Non-serious adverse events were significantly greater in the F(ab')₂ group (10 vs. 1 event; p < 0.01).

Patients treated with F(ab')₂ antivenom for North American pit viper envenomation required less doses to achieve initial control, but experienced a greater incidence of non-serious adverse events.