Effectiveness of snake antivenom: Species and regional venom variation and its clinical impact

Abstract

The ubiquity of venom variation in snakes poses special problems for the manufacture of antivenom and has undermined the commercial attractiveness of this class of therapeutic agent. In particular, it has been amply documented that both interspecific and intraspecific variation in venom composition can affect the neutralisation capacity of antivenoms. This may be exacerbated by the selective use of tests of venom toxicity and antivenom efficacy, such as the lethal dose and ED50, resulting in inadequate neutralisation of time, rather than dose, dependent toxins, particularly enzymes involved in defibrinogenating, haemorrhagic and necrotising venom activities. The clinical consequences can be reduced efficacy against some important venom activities or even complete treatment failure in critical envenomations. All these factors, combined with the ongoing reduction in the number of antivenom manufacturers world-wide, and concomitant contraction in the range of available antivenoms, present significant challenges for the treatment of snakebite in the 21st century.