A Comparison of Crotalinae Equine Immune F(ab)2 Antivenom (Anavip) and Crotalidae Polyvalent Immune Fab,
Condition: Snake Bite; Blood Coagulation Disorders
MeSH terms: Hemostatic Disorders; Blood Coagulation Disorders; Snake Bites
Intervention: Anavip; CroFab
Intervention description: Anavip, 10 vials Intravenous (IV) every 2 hours until initial control has been achieved; then 3 maintenance doses of 4 vials every 6 hrs; CroFab, 5 vials Intravenous (IV) every 2 hours until initial control has been achieved; then 3 maintenance doses of 2 vials every 6 hrs
Intervention MeSH terms: Antivenins
Phase: Phase 2
Study type: Interventional
Primary purpose: Treatment
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Enrollment: 12.0
Sex: All
Minimum age: 18 Years
Maximum age: 70 Years
Healthy volunteers: No
Keywords: Snake Bite; Venom and antivenom kinetics

Summary:

      This phase II study was a prospective, randomized, open-label, multi-center study in the
      United States, involving patients from 18 to 70 years of age, comparing Anavip (Antivenin
      Crotalinae [pit viper] equine immune F(ab)2; Instituto Bioclon, Mexico City, Mexico) against
      CroFab (Protherics Inc., Nashville, Tennessee), the only currently approved product for
      treatment of Crotalinae (pit viper) envenomation in the US.

      The study was designed to evaluate the hypothesis that lasting correction of snakebite
      induced thrombocytopenia and hypofibrinogenemia are possible following correction with F(ab)2
      antivenom, by analyzing in detail the relationships among platelet count, fibrinogen, venom
      levels, and antivenom levels in subjects presenting with thrombocytopenia following crotaline
      viper envenomation. In the study we expected to see a fall in platelet count following Fab
      treatment, commensurate with that reported in the past. We hypothesized that following F(ab)2
      treatment there would be a slower drop in post-treatment platelet counts, with a relatively
      higher platelet count at any given point in the follow-up period. We further hypothesized
      that an initial rise and later fall in platelet count would correspond with rise and fall in
      antivenom levels, and would be mirrored by concurrent drop and rise in levels of unbound
      circulating venom.
    

Eligibility criteria:

        Inclusion Criteria:

          -  men and women 18 to 70 years of age

          -  presenting for emergency treatment of pit viper bite

          -  informed consent document read and signed by subject

        Exclusion Criteria:

          -  allergy to horse serum, sheep serum, or papaya

          -  current use of any antivenom, or use within the last month

          -  current participation in a clinical drug study, or participation within the last month

          -  pregnancy or breast-feeding

          -  underlying medical conditions that significantly alter blood coagulation:
             thrombocytopenia, hemophilia, familial dysfibrinogenemia, leukemia, recent ingestion
             of superwarfarin compounds (rat poison)

          -  use of any medication expected to affect platelet count, coagulation factors, or
             fibrinogen: chemotherapeutic agents, warfarin, heparin, aspirin

          -  No clinical indications of snake bite envenomation