Crotalus atrox antivenin



Crotalus atrox antivenin is a mixture of antibodies used to treat venomous snake bites from Crotalus atrox (Western Diamondback rattlesnake).

Brand Names
Generic Name
Crotalus atrox antivenin
DrugBank Accession Number

Each year it is estimated there are 45,000 snakebites in the US and 300,000 to 400,000 bites worldwide. About 8000 of these snakebites involve venomous snake species. The majority of people bitten are males and about 50% occur in the age group of 18 to 28 10.

Crotalus atrox antivenin is derived and purified immunoglobulin fragments obtained from other domestic animals such as sheep previously immunized with Crotalus atrox (Western Diamondback rattlesnake). Bites from this snake are the most common in the state of Texas, USA 3.

The final purified antivenin product is produced by mixing other different monospecific snake antivenins and isolating the antivenin of interest through fractionation and chromatography techniques. It is intravenously (IV) administered to prevent/limit systemic toxicity Label.

Approved, Experimental
Biologic Classification
Protein Based Therapies
Other protein based therapies
Protein Chemical Formula
Not Available
Protein Average Weight
Not Available
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  • Crotalus atrox immune fab antivenin (ovine)



CROFAB is indicated for the management of adult and pediatric patients with North American crotalid envenomation. The term crotalid is used to describe the Crotalinae subfamily (formerly known as Crotalidae) of venomous snakes which includes rattlesnakes, copperheads and cottonmouths/water moccasins Label.

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Associated Conditions
Contraindications & Blackbox Warnings
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Crotalus atrox venom contains agents that render human fibrinogen and plasma incoagulable by thrombin 4. CROFAB antivenom reverses these effects Label.

This facilitates re-distribution of venom toxins away from target tissues and elimination from the body 8.

It is a mixture of 4 different monospecific antivenoms derived from serum of healthy sheep immunized with one of the following North American snake venoms: C. atrox (Western diamondback rattlesnake), C. adamanteus (Eastern diamondback rattlesnake), C. scutulatus (Mojave rattlesnake), or A. piscivorus (cottonmouth or water moccasin) 8.

Mechanism of action

CROFAB consists of venom-specific Fab fragments of immunoglobulin G (IgG) that work by binding to and neutralizing venom toxins, facilitating their redistribution away from target tissues and their elimination from the body 6.

CROFAB contains only the Fab fragments from ovine-derived immunoglobulins. The enzyme papain is used to cleave the IgG antibody, creating 2 separate Fab fragments and 1 Fc fragment. After the cleavage step, another protein binds to the Fc fragments, which are not essential for binding snake venom, allowing the pure Fab fragments to be recovered.The Fab fragments of an immunoglobulin contain the variable regions that recognize and bind to specific antigens 6.


Not Available

Volume of distribution

Not Available

Protein binding

Not Available

Not Available
Route of elimination

Not Available


12-23 hours 10


Not Available

Adverse Effects
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Most common adverse reactions (incidence ≥5% of subjects) were urticaria, rash nausea, pruritus and back pain Label.

Severe hypersensitivity reactions may occur with the use of CROFAB. In case of acute hypersensitivity reactions, including anaphylaxis and anaphylactoid reactions, discontinue infusion and institute appropriate emergency treatment Label.

CROFAB contains purified immunoglobulin fragments from the blood of sheep that have been immunized with snake venoms. Injection of heterologous animal proteins can lead to severe acute and delayed hypersensitivity reactions (late serum reaction or serum sickness) and a possible febrile response to immune complexes formed by animal antibodies and neutralized venom components.

Papain enzyme is used to cleave antibodies into fragments during the processing of CROFAB, and negligible amounts of papain or inactivated papain residues may be present. Patients allergic to papain, chymopapain, other papaya extracts, or the pineapple enzyme bromelain may also have an allergic reaction to CROFAB. Certain dust mite allergens and some latex allergens share antigenic structures with papain and patients with these allergies may be allergic to papain Label.

Not Available
Pharmacogenomic Effects/ADRs
Not Available


Drug Interactions
This information should not be interpreted without the help of a healthcare provider. If you believe you are experiencing an interaction, contact a healthcare provider immediately. The absence of an interaction does not necessarily mean no interactions exist.
Not Available
Food Interactions
No interactions found.


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Mixture Products
NameIngredientsDosageRouteLabellerMarketing StartMarketing EndRegionImage
CroFabCrotalus atrox antivenin (1 g/1) + Agkistrodon piscivorus antivenin (1 g/1) + Crotalus adamanteus antivenin (1 g/1) + Crotalus scutulatus antivenin (1 g/1)Injection, powder, lyophilized, for solutionIntravenousBTG International Inc.2000-02-10Not applicableUS flag


Drug Categories
Chemical TaxonomyProvided by Classyfire
Not Available
Organic Compounds
Super Class
Organic Acids
Carboxylic Acids and Derivatives
Sub Class
Amino Acids, Peptides, and Analogues
Direct Parent
Alternative Parents
Not Available
Not Available
Molecular Framework
Not Available
External Descriptors
Not Available
Affected organisms
  • Humans

Chemical Identifiers

CAS number
Not Available


General References
  1. de Rezende NA, Torres FM, Dias MB, Campolina D, Chavez-Olortegui C, Amaral CF: South American rattlesnake bite (Crotalus durissus SP) without envenoming: insights on diagnosis and treatment. Toxicon. 1998 Dec;36(12):2029-32. [Article]
  2. Seifert SA, Boyer LV, Dart RC, Porter RS, Sjostrom L: Relationship of venom effects to venom antigen and antivenom serum concentrations in a patient with Crotalus atrox envenomation treated with a Fab antivenom. Ann Emerg Med. 1997 Jul;30(1):49-53. [Article]
  3. Rosen PB, Leiva JI, Ross CP: Delayed antivenom treatment for a patient after envenomation by Crotalus atrox. Ann Emerg Med. 2000 Jan;35(1):86-8. [Article]
  4. Pandya BV, Budzynski AZ: Anticoagulant proteases from western diamondback rattlesnake (Crotalus atrox) venom. Biochemistry. 1984 Jan 31;23(3):460-70. [Article]
  5. Delayed antivenom treatment for a patient after envenomation by Crotalus atrox [Link]
  6. CROFAB.COM [Link]
  7. Epocrates online, Crofab [Link]
  8., Crofab [Link]
  9. Crotalus atrox PhospholipaseAz [File]
  10. Crotalidae Polyvalent Immune Fab (Ovine) [File]
PubChem Substance
FDA label
Download (407 KB)

Clinical Trials

Clinical Trials
4CompletedTreatmentSnake Bite1
4TerminatedTreatmentSnake Envenomation1
3CompletedTreatmentSnake Bite1
2CompletedTreatmentCoagulation Disorder / Snake Bite1


Not Available
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Dosage Forms
Injection, powder, lyophilized, for solutionIntravenous
Not Available
Not Available


Not Available
Experimental Properties
Not Available


Pharmacological action
General Function
Phospholipase activity
Specific Function
PA2 catalyzes the calcium-dependent hydrolysis of the 2-acyl groups in 3-sn-phosphoglycerides. Has a powerful potency for releasing arachidonic acid from cell membrane phospholipids. Prefers phosph...
Gene Name
Uniprot ID
Uniprot Name
Group 10 secretory phospholipase A2
Molecular Weight
18153.04 Da
  1. Walton RM, Brown DE, Hamar DW, Meador VP, Horn JW, Thrall MA: Mechanisms of echinocytosis induced by Crotalus atrox venom. Vet Pathol. 1997 Sep;34(5):442-9. doi: 10.1177/030098589703400508. [Article]
  2. Sanny CG: In vitro evaluation of total venom-antivenin immune complex formation and binding parameters relevant to antivenin protection against venom toxicity and lethality based on size-exclusion high-performance liquid chromatography. Toxicon. 2011 May;57(6):871-81. doi: 10.1016/j.toxicon.2011.03.003. Epub 2011 Mar 15. [Article]
  3. Perumal Samy R, Gopalakrishnakone P, Chow VT: Therapeutic application of natural inhibitors against snake venom phospholipase A(2). Bioinformation. 2012;8(1):48-57. doi: 10.6026/97320630008048. Epub 2012 Jan 6. [Article]

Drug created at September 08, 2017 20:22 / Updated at June 19, 2021 00:27