Phase 3 Multicenter Comparative Study to Confirm Safety and Effectiveness of the F(ab)2 Antivenom Anavip.

Inclusion Criteria: * Men and women 2 to 80 years of age * Presenting for emergency treatment of pit viper bite * Informed consent document read and signed by patient (or parent/legal guardian) Exclusion Criteria: * Current use of any antivenom, or use within the last month * Current participation in a clinical drug study, or participation within the last month * Positive urine or blood pregnancy test at screening * Breast-feeding * Allergy to horse serum, sheep serum, or papaya * Underlying medical conditions that significantly alter platelet count or fibrinogen; thrombocytopenia, hemophilia, familial dysfibrinogenemia, leukemia * Use of any medication expected to affect platelet count, coagulation factors or fibrinogen: chemotherapeutic agents, warfarin, heparin * No clinical indications of snake bite requiring antivenom for treatment