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INTRODUCTION

The terms “antivenom” and “antivenin” often are used interchangeably. Although the origin of the term “antivenom” is obvious, “venin” is French for venom and “antivenin” is traditionally used in certain parts of the world. Wyeth Pharmaceuticals, the maker of Crotaline and Micrurus antivenom, and Merck & Co, Inc, the maker of Latrodectus antivenom, adopted “antivenin” in the brand names for their products. Brand name recognition was largely responsible for the use of the term “antivenin” in place of “antivenom.” In 1981, the World Health Organization determined the preferred terms for the English language to be “venom” and “antivenom.”

HISTORY

Two of the most notable genera of spiders of medical importance in the United States are Latrodectus (L. mactans, L. geometricus, L. variolus, L. hesperus, and L. bishopi are native, whereas L. geometricus was introduced) and Loxosceles. Commercially available antivenom does not exist in the United States for treatment of Loxosceles envenomation. Currently, there is one commercially available Latrodectus antivenom in the United States. Black Widow Spider Antivenin (Merck & Co, Inc) (Merck BW-AV) has been available in the United States since its US Food and Drug Administration (FDA) approval in 1936.3 The use of this antivenom in the treatment of Latrodectus envenomations remains controversial, as mortality from these bites is low in the United States,8,9,31,33 and complications including death following antivenom administration are rarely reported.8,22,32 Ongoing research and development of an F(ab′)2 antivenom may ameliorate concerns and limitations related to potential adverse events resulting from administration of the Merck antivenom and production shortages limiting availability.12 As of June 2018, however, F(ab′)2 black widow antivenom has not been approved for use by the US Food and Drug Administration (FDA) but is in clinical trials under the trade name Analatro.

PHARMACOLOGY

Chemistry, Preparation, and Mechanism of Action

Antivenom for spiders is prepared in a similar manner as other antivenom products by first immunizing animals with nontoxic amounts of venom.5,26 Monkeys, horses, goats, sheep, chicken, camels, and rabbits have been used historically to source antivenom.29 The animals are placed on an inoculation schedule to allow gradual production of immunoglobulins, most importantly IgG. Sufficient antibody production usually occurs within 6 weeks. The species availability, financial considerations, and tradition rather than scientific modeling is typically responsible for animal choice for immune serum production. The majority of antivenom producers use horses, since they are relatively easy to maintain, and large volumes of serum can be obtained at one time without harming the animal. During antivenom production varying efforts are made to remove animal proteins such as albumin. Antivenoms target, bind, neutralize, and promote elimination or redistribution of toxins from body tissues. To date, no studies have compared immune sera of different animals for human ...

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