Scorpion (centruroides) immune Fab2 antivenin (equine)



Scorpion (centruroides) immune Fab2 antivenin (equine) is a purified preparation of immunoglobulin gamma antibodies used to treat scorpion stings.

Brand Names
Generic Name
Scorpion (centruroides) immune Fab2 antivenin (equine)
DrugBank Accession Number

Centruroides (scorpion) Immune F(ab')2 (equine) is a purified preparation of immune globulin F(ab’)2 fragments that are derived from plasma of the horses immunized with venom of C. noxius, C. l. limpidus, C. l. tecomanus, and C. s. suffusus. It is intravenously administered patients with clinical signs of scorpion envenomation so that the Fab fragments bind to the toxins and limit systemic toxicity. It was approved by FDA in 2011 and is marketed under the name Anascorp 4.

Anascorp is produced from equine IgG antibodies. Because initial development and use of this product in Mexico, venoms from several Centruroides species endemic to Mexico are pooled and diluted 14.

This drug is a polyvalent antivenin proven to be useful against scorpion stings. It is the first specific treatment to neutralize toxin from Centruroides scorpion stings, particularly those of the Centruroides sculpturatus in the United States 13.

Envenomation by a scorpion sting can result in serious cardiovascular effects 2. Severe scorpion stings may cause loss of muscle control and respiratory failure, warranting heavy sedation and hospitalization in an intensive care unit. Most commonly, children experience severe reactions, however, adults can be affected, too 3, 4, 6.

Biologic Classification
Protein Based Therapies
Other protein based therapies
Protein Chemical Formula
Not Available
Protein Average Weight
Not Available
Not Available
  • Antivenin, scorpion
  • Antivenin,centruroides immune Fab2
  • Centruroides (scorpion) Immune F(ab')2 (equine)
  • Centruroides (scorpion) immune F(ab')2 (equine) injection
  • Centruroides (scorpion) immune F(ab)2 intravenous (equine)
  • Centruroides (scorpion) immune Fab2 (equine)
  • Centruroides antivenin
  • Centruroides antivenin (equine)
  • Centruroides Fab2 antivenin (equine)
  • Centruroides suffusus suffusus) (equine)
  • Mexican scorpion (centruroides) Fab2 antivenin (equine)
  • Polyvalent mexican scorpion antivenin (horse)
  • Scorpion (centruroides) Fab2 immunoglobulin (equine)



Indicated for treatment of clinical signs of scorpion envenomation 3, 4.

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In 2008, 15 522 scorpion envenomations were reported to the National Poison Data System in the USA, with one fatality ocurring in a toddler. In the United States, Centruroides sculpturatus, commonly known as the Arizona bark scorpion, is the only scorpion species whose venom is toxic to humans. Though most Centruroides scorpion stings in adults are well-tolerated with minimal effects, pediatric patients are quite susceptible to signicant morbidity from the venom 14.

In a pharmacokinetic study of 1534 patients, 95-100% of the study group were relieved of systemic signs associated with scorpion envenomation in less than four hours after initiating Anascorp treatment. In the historical control database, only 3.1% of patients experienced relief of symptoms within 4 hours of hospital admission Label. Clinical manifestations of scorpion sting and envenomation include sweating, salivation, cool extremities, priapism, hypertension or hypotension, and tachycardia 9.

In 1396/1534 patients, the average time from the start of Anascorp infusion to the resolution of clinical signs and symptoms of envenomation was 1.42 hours (0.2 to 20.5 hours). Pediatric patients were found to experience a slightly faster time to resolution (1.28 ± 0.8 hours) compared to that of adult patients (1.91 ±1.4 hours). The time to resolution of symptoms was not affected by use of sedatives (474 patients who received sedatives resolved in 1.49 ± 1.1 hours and 922 patients who did not receive sedatives resolved in 1.38 ± 0.9 hours) Label.

Mechanism of action

Anascorp, the trade name of this drug, is composed of venom-specific F(ab’)2 fragments of immunoglobulin G (IgG) that bind to and neutralize venom toxins, promoting redistribution away from target tissues and subsequent elimination from the body Label.


Not Available

Volume of distribution

Steady state: 13.6 ± 5.4 L Label.

Protein binding

Not Available

Not Available
Route of elimination

Not Available


159 ± 57 h Label.


83.5 ± 38.4 ml/Hr Label

Adverse Effects
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The most common adverse reactions observed in ≥ 2% of patients in the clinical studies for Anascorp were: vomiting, pyrexia, rash, nausea, and pruritus Label.

Severe hypersensitivity reactions, including anaphylaxis, may occur with Anascorp 10, Label. Diligent patient monitoring for hypersensitivity reactions and preparation for intravenous therapy using epinephrine, corticosteroids, and diphenhydramine hydrochloride is recommended during the infusion. If an anaphylactic reaction occurs during the Anascorp infusion, case administration immediately, and administer warranted emergency medical care Label.

Patients with existing allergies to horse protein are at a higher risk for developing anaphylactic reactions. Patients who have had previous therapy with Anascorp or another equine antivenom/antitoxin may have become sensitized to equine proteins and be at an elevated risk for a severe hypersensitivity reaction Label.

Trace amounts of cresol from the manufacturing process are contained in Anascorp. Localized reactions and generalized myalgias have been observed with the use of cresol as an injectable excipient Label.

Monitor patients with follow-up visit(s) for signs and symptoms of delayed allergic reactions or serum sickness (symptoms include rash, fever, myalgia, arthralgia), and treat appropriately if necessary. Eight out of 1,534 (0.5%) patients in the clinical trials exhibited symptoms suggestive of serum sickness Label.

Anascorp is created from equine (horse) plasma, it may carry a risk of transmitting infectious agents, e.g., viruses Label.

The following adverse reactions have been identified during post-approval use of Anascorp: chest tightness, palpitations, rash, and pruritus. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure 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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Brand Name Prescription Products
NameDosageStrengthRouteLabellerMarketing StartMarketing EndRegionImage
AnascorpInjection, powder, lyophilized, for solution7.0 mg/1mLIntravenousRare Disease Therapeutics, Inc2011-08-03Not applicableUS flag
Unapproved/Other Products
NameIngredientsDosageRouteLabellerMarketing StartMarketing EndRegionImage
ACSERA 5 ML ENJEKSIYONLUK COZELTI KONSANTRESI ICEREN FLAKONScorpion (centruroides) immune Fab2 antivenin (equine) (100 IU/5mL)InjectionIntramuscular; Intravenous; SubcutaneousVETAL SERUM VE BİYOLOJİK ÜRÜNLER ÜRETİMİ SAN. VE TİC. A.Ş.2020-08-14Not applicableTurkey 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 and other mammals

Chemical Identifiers

CAS number
Not Available


General References
  1. Sanaei-Zadeh H: Hypersensitivity reaction to scorpion antivenom. Indian Dermatol Online J. 2014 Nov;5(Suppl 1):S51-2. doi: 10.4103/2229-5178.144536. [Article]
  2. Bawaskar HS, Bawaskar PH: Efficacy and safety of scorpion antivenom plus prazosin compared with prazosin alone for venomous scorpion (Mesobuthus tamulus) sting: randomised open label clinical trial. BMJ. 2011 Jan 5;342:c7136. [Article]
  3. Antidote Relieves Scorpion Stings [Link]
  4. Anascorp [Link]
  5. Scorpion antivenin approved [Link]
  6. FDA Approves First-Ever Antivenom for Scorpion Stings [Link]
  7. Efficacy and safety of scorpion antivenom plus prazosin compared with prazosin alone for venomous scorpion (Mesobuthus tamulus) sting: randomised open label clinical trial [Link]
  8. Management of scorpion envenoming: a systematic review and meta-analysis of controlled clinical trials [Link]
  9. Emerging options for the management of scorpion stings [Link]
  10. Hypersensitivity reaction to scorpion antivenom [Link]
  11. Adverse reactions to snake antivenom, and their prevention and treatment [Link]
  12. Centruroides (Scorpion) Immune F(ab′)2 (Equine) [Link]
  13. PDR drug reference [Link]
  14. Utah poison control [Link]
PubChem Substance
FDA label
Download (142 KB)

Clinical Trials

Clinical Trials
3CompletedTreatmentScorpion Sting Envenomation1
3CompletedTreatmentScorpion Stings1
2, 3CompletedTreatmentScorpion Sting Envenomation2


Not Available
Not Available
Dosage Forms
InjectionIntramuscular; Intravenous; Subcutaneous100 IU/5mL
Injection, solutionIntravenous
Injection, powder, lyophilized, for solutionIntravenous7.0 mg/1mL
Not Available
Not Available


Not Available
Experimental Properties
Not Available

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