ABSTRACT
Besides the snakes there exist only two venomous lizard species in the reptile order Squamata: Heloderma suspectum and Heloderma horridum which belong to the unique family Helodermatidae. The lizards produce a powerful venom which has lethal potency. In almost all cases of human envenoming the lizard had been provoked or handled carelessly. The venom of Heloderma is similar in composition and lethality for both species and represents a mixture of proteins and peptides. Very active kallikreins have been isolated from both Heloderma suspectum and Heloderma horridum venom; the enzyme from the latter venom was named helodermatine. Holding on during the bite facilitates the introduction of the venom into the puncture wound; the longer the bite the more severe is the envenoming. The most important measure, which is often difficult to achieve, is to remove the lizard from the bite site where it firmly holds on.
