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A case of significant coagulopathic envenoming from Bothrops asper: Appropriate antivenom use and therapeutic response


Keyler, Daniel E.


Department of Experimental & Clinical Pharmacology

University of Minnesota

Minneapolis, Minnesota USA


Division of Clinical Pharmacology & Toxicology

Department of Medicine

Hennepin County Medical Center (retired)

Minneapolis, Minnesota USA



Barden, Carl

Roberts, Mara

Medtoxin Venom Laboratories

Deland, Florida, USA


Terciopelo (Bothrops asper), a velvet-earth-toned pit viper, is indigenous from Mexico's southeastern coasts down through Central America to the northwestern coasts of South America. The species is also maintained in specialized US laboratories where venom is collected and supplied for use in biomedical research and immunogen use in antivenom production. The snake is known for its volatile temperament and delivering severe bites, making it a challenging species to confront in any setting. Toxicological consultation cases of envenoming by B. asper in the United States are uncommon. On June 21, 2024, an adult female professional herpetologist was standing on tip toes and peeking over an upper cage drawer containing an 18-inch juvenile. The snake was facing away toward the back when it immediately turned, striking the herpetologist's upper lip. Transport to the emergency department followed. Examination of the lip one hour post bite showed two fang punctures, erythema, and swelling. Development of profound tissue damage to the highly vascular and innervated lip was a major concern. Laboratory values confirmed acute coagulopathy: fibrinogen (Fib) <60 mg/dL, INR >16, prothrombin Time (PT) >130 sec, partial thromboplastin time (PTT) 69 sec, and platelets normal. Administration of 10 vials of F(ab')2 antivenom (Anavip; produced using B. asper venom as immunogen) was initiated within one hour of the bite. Over the following eleven hours two more 10-vial rounds of antivenom was administered (without adverse effects) resulting in all coagulation values returning to normal. Ontogenic variation studies of juvenile vs adult B. asper venom composition revealed that the venom-induced pathophysiological actions of juvenile venom cause greater coagulopathic effects than that of adults, which is reflected in this case. The use of appropriate antivenom, its timely administration, and correct dosing confirmed pharmacotherapeutic efficacy in this case. Tissue damage remained minimal and patient symptoms resolved within one month.

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