Centruroides (Scorpion) Immune F(ab′)2 (Equine)
Class: Antitoxins and Immune Globulins
VA Class: IM300
Medically reviewed on April 26, 2018.
Antivenom; equine IgG F(ab′)2 fragments capable of binding and neutralizing venom toxins of Centruroides scorpions.1 5
Uses for Centruroides (Scorpion) Immune F(ab′)2 (Equine)
Treatment of clinical signs of scorpion envenomation;1 2 designated an orphan drug by FDA for this use.2
May shorten time to resolution of envenomation symptoms,1 5 possibly eliminating need for treatment in an intensive care unit.5
In the US, Centruroides sculpturatus (commonly known as the bark scorpion) is the only scorpion considered potentially dangerous to humans;3 4 8 14 15 found mainly in Arizona, but may be found in parts of California, New Mexico, Texas, Nevada, and northern Mexico.3 4 8 15
Consider consultation with experts experienced in treating Centruroides envenomation (e.g., Arizona Poison and Drug Information Center in Tucson, Banner Good Samaritan Poison and Drug Information Center in Phoenix).15
Centruroides (Scorpion) Immune F(ab′)2 (Equine) Dosage and Administration
Initiate treatment as soon as possible after a scorpion sting in patients who develop clinically important signs of scorpion envenomation (e.g., loss of muscle control, roving or abnormal eye movements, slurred speech, respiratory distress, excessive salivation, frothing at the mouth, vomiting).1
Monitor closely during and for up to 1 hour after completion of IV infusion to confirm resolution of clinically important signs of envenomation.1
Administer by IV infusion.1
Reconstitution and Dilution
Reconstitute each vial of lyophilized Centruroides (scorpion) immune F(ab′)2 (equine) with 5 mL of 0.9% sodium chloride; mix using continuous gentle swirling.1 When multiple vials are indicated (e.g., for initial dose), combine required number of reconstituted vials immediately following reconstitution.1
Prior to infusion, dilute total dose (total combined reconstituted vials) to a total volume of 50 mL using 0.9% sodium chloride.1
Rate of Administration
Administer by IV infusion over 10 minutes.1
Dosage expressed in terms of number of vials.1
Initially, 3 vials.1
Give additional 1-vial doses every 30–60 minutes as needed.1
Initially, 3 vials.1
Give additional 1-vial doses every 30–60 minutes as needed.1
No special population dosage recommendations.1
Cautions for Centruroides (Scorpion) Immune F(ab′)2 (Equine)
Manufacturer states none.1
Severe hypersensitivity reactions, including anaphylaxis, may occur.1
Patients with known allergies to equine protein are at increased risk for anaphylactic reactions.1 Patients who previously received Centruroides (scorpion) immune F(ab′)2 (equine) or another equine antivenom or antitoxin may be at increased risk for severe hypersensitivity reactions.1
Monitor closely for hypersensitivity during antivenom infusion; IV epinephrine, corticosteroids, and diphenhydramine should be readily available.1 6
If anaphylactic reaction occurs, immediately discontinue antivenom infusion and initiate appropriate emergency medical care.1
Delayed Hypersensitivity or Serum Sickness Reactions.
Delayed hypersensitivity or serum sickness reactions may occur.1 Mild symptoms may include pruritus, nausea, urticaria, low-grade fever, and malaise; severe manifestations include persistent urticaria, vomiting, arthralgia, myalgia, syncope, and angioedema.6
Monitor for manifestations of delayed allergic reactions or serum sickness (e.g., rash, fever, myalgia, arthralgia) at follow-up visits.1 Treat such reactions as necessary;1 treatment is generally symptomatic (e.g., antihistamines, analgesics, antipyretics, corticosteroids).6
Risk of Transmissible Infectious Agents
Prepared from equine plasma;1 potentially may transmit infectious agents, including viruses.1 Several steps in manufacturing process (e.g., pepsin digestion, ammonium sulfate precipitation/heat treatment, nanofiltration) reduce risk of transmission of viruses.1
Contains trace amounts of cresol (<0.41 mg per vial) from manufacturing process.1 Cresol used as an injectable excipient has resulted in localized reactions and generalized myalgia.1
Not known whether distributed into milk.1 Use with caution in nursing women.1
Efficacy and safety in pediatric patients comparable to that in adults.1 Has been used in children ranging from younger than 1 month to 18 years of age.1
Efficacy and safety in geriatric patients not studied specifically; considered comparable to that in overall patient population.1
Common Adverse Effects
Vomiting, pyrexia, rash, nausea, pruritus.1
Interactions for Centruroides (Scorpion) Immune F(ab′)2 (Equine)
No formal drug interaction studies to date.1
Centruroides (Scorpion) Immune F(ab′)2 (Equine) Pharmacokinetics
Following IV infusion, clinically important manifestations of scorpion envenomation generally resolve within 4 hours.1 5
Approximately 6.6 days in healthy (nonenvenomed) adults.1 13 Additional study needed to determine pharmacokinetics in patients with scorpion envenomation.13
For Injection, for IV Use
Room temperature (up to 25°C); may be exposed to temperatures up to 40°C.1 Do not freeze.1 Discard partially used vials.1
Centruroides (scorpion) immune F(ab′)2 (equine) is a polyvalent preparation of venom-specific F(ab′)2 fragments of equine IgG that bind and neutralize Centruroides venom toxins, facilitating redistribution of the venom away from target tissues and elimination from the body.1
Manufactured from plasma of horses immunized with venom of C. noxius, C. limpidus limpidus, C. limpidus tecomanus, and C. suffusus suffusus.1 Although C. sculpturatus venom not used in manufacturing process, in vitro studies demonstrate similar binding affinities and high degree of cross-reactivity among venoms of the various Centruroides species, including C. sculpturatus.4 5 11
Standardized by ability to neutralize Centruroides scorpion venom in mice (mouse LD50 neutralizing units).1 Each commercially available vial will neutralize ≥150 mouse LD50 units of Centruroides venom.1
Advice to Patients
Importance of immediately contacting clinician or seeking emergency treatment if manifestations of delayed allergic reactions or serum sickness (e.g., rash, pruritus, joint pain, arthralgia, fever, lymphadenopathy, malaise) develop within 14 days following hospital discharge.1 (See Delayed Hypersensitivity or Serum Sickness Reactions under Cautions.)
Importance of women informing clinicians if they are pregnant or breast-feeding.1
Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses.1
Importance of informing patients of other important precautionary information.1 (See Cautions.)
Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.
Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.
For injection, for IV use
Rare Diseases Therapeutics
AHFS DI Essentials. © Copyright 2018, Selected Revisions April 26, 2012. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814.
1. Rare Diseases Therapeutics. Anascorp [Centruroides (scorpion) immune F(ab′)2 (equine) injection] prescribing information. Franklin, TN. 2011 Jul.
2. Food and Drug Administration. FDA Application: Search Orphan Drug Designations and Approvals. Rockville, MD. From FDA website. Accessed 2011 Dec 1.
3. Curry SC, Vance MV, Ryan PJ et al. Envenomation by the scorpion Centruroides sculpturatus. J Toxicol Clin Toxicol. 1983-1984; 21:417-49.
4. Bernstein JN. Antivenom (Scorpion and Spider). In: Flomenbaum NE, Goldfrank LR, Hoffman RS et al, eds. Goldfrank’s toxicologic emergencies. 8th ed. New York: McGraw-Hill; 2006:1623-7.
5. Boyer LV, Theodorou AA, Berg RA et al. Antivenom for critically ill children with neurotoxicity from scorpion stings. N Engl J Med. 2009; 360:2090-8. [PubMed 19439743]
6. Heard K, O'Malley GF, Dart RC. Antivenom therapy in the Americas. Drugs. 1999; 58:5-15. [PubMed 10439926]
7. Gibly R, Williams M, Walter FG et al. Continuous intravenous midazolam infusion for Centruroides exilicauda scorpion envenomation. Ann Emerg Med. 1999; 34:620-5. [PubMed 10533010]
8. Likes K, Banner W, Chavez M. Centruroides exilicauda envenomation in Arizona. West J Med. 1984; 141:634-7. [PubMed 6516334]
9. Gateau T, Bloom M, Clark R. Response to specific Centruroides sculpturatus antivenom in 151 cases of scorpion stings. J Toxicol Clin Toxicol. 1994; 32:165-71. [PubMed 8145356]
10. Arizona Poison & Drug Information Center. Scorpions. Phoenix, AZ. 2011 Feb. From website. Accessed 2011 Dec 1.
11. Chase P, Boyer-Hassen L, McNally J et al. Serum levels and urine detection of Centruroides sculpturatus venom in significantly envenomated patients. Clin Toxicol (Phila). 2009; 47:24-8. [PubMed 18763156]
13. Vázquez H, Chávez-Haro A, García-Ubbelohde W et al. Pharmacokinetics of a F(ab')2 scorpion antivenom in healthy human volunteers. Toxicon. 2005; 46:797-805. [PubMed 16197974]
14. Chippaux JP, Goyffon M. Epidemiology of scorpionism: a global appraisal. Acta Trop. 2008; 107:71-9. [PubMed 18579104]
15. Suchard J. Scorpion envenomation. In: Auerbach PS. Wilderness medicine. 6th ed. Philadelphia, PA: Mosby Elsevier; 2012. From MedicinesComplete website. Accessed 2012 Feb 21.
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