Scorpion Anti-venum

In August of 2011, the US Food and Drug Administration approved Anascorp®, the first specific treatment for scorpion stings by Centruroides scorpions in the United States.  Anascorp®, Centruroides (Scorpion) Immune F(ab’)2 (Equine) Injection, is made from the plasma of  horses immunized with scorpion venom.  The venom-specific F(ab’)2 fragments of immunoglobulin G (IgG) bind and neutralized venom toxins, facilitating elimination from the body. 

 

Treatment with Anascorp® should be initiated as soon as possible after the scorpion sting in patients who develop clinically important signs of scorpion envenomation, including but not limited to loss of muscle control, roving or abnormal eye movements, slurred speech, respiratory distress, excessive salivation, frothing at the mouth, or vomiting.

 

Dosage and Administration:

Initial Dose

3 vials

·                                                                                                           Reconstitute each vial with 5 mL of normal saline and mix by gentle swirling

·                                                                                                           Combine the contents of the reconstituted vials promptly and further dilute to a total of 50 mL with normal saline

·                                                                                                           Infuse intravenously over 10 minutes

 

The safety and efficacy of Anascorp® was assessed in a prospective double-blinded randomized placebo-controlled study, four open-label studies and one retrospective study in various treatment settings in the United States and Mexico, where scorpion envenomation is common. In total, 1534 patients ranging from less than one month to 90 years old were treated. The majority of patients (78%) were pediatric, ranging from less than one month to 18.7 years of age. Treatment success was determined by resolution of clinically important signs of scorpion envenomation within four hours of starting infusion. The randomized placebo-controlled study enrolled 15 subjects, eight to the Anascorp® treated group and seven to the placebo. The symptom resolution success rate was 100% for the Anascorp® treated and 14.3% for the placebo group.

 

Since Anascorp® is made from the plasma of horses, a serious and severe hypersensitivity reaction, including anaphylaxis can occur.  Therefore, it is important to monitor each patient for allergic reactions, particularly in patients with a history of hypersensitivity to horse proteins or patients who have received previous therapy with antivenoms containing horse proteins.  If an anaphylactic reaction occurs during the infusion, stop the infusion immediately and administer appropriate emergency medical care.  Furthermore, it is possible for a patient to experience delayed allergic reactions or serum sickness (rash, fever, myalgia, arthralgia).  Eight out of 1,534 (0.5%) patients in the clinical trials exhibited symptoms suggestive of serum sickness.  The most common adverse reactions observed in ≥ 2% of patients in the clinical studies for Anascorp® were: vomiting, pyrexia, rash, nausea, and pruritus.

 

Most stings to healthy, young adults can be managed at home with basic first aid and follow-up.  Victims should:

  • clean the site with soap and water
  • apply a cool compress
  • elevate the affected limb to the same level as your heart
  • take aspirin or acetaminophen as need for minor discomfort

 JR Rotoso

References:

1.       Krifi M.H, Savin S, Debray M, Bon C, Ayeb M.E, Choumet V. Pharmacokinetic studies of scorpion venom before and after antivenom immunotherapy. Toxicon, 2005;45:187–198.

2.       Curry SC, Vance MV, Ryan PJ, Kunkel DB, Northey WT. Envenomation by the scorpion Centruroides sculpturatus, J Toxicol Clin Toxicol, 1983-1984;21(4-5):417-49.

3.       Boyer LV, Theodorou AA, Berg RA, Mallie J. Antivenom for Critically Ill Children with Neurotoxicity from Scorpion Stings. N Engl J Med, 2009;360:2090-8.

4.       FDA Approves First Scorpion Sting Antidote.  Food and Drug Administration Web Site.  Available at: http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm266515.htm.  Accessed November 19, 2011.

                5.       Anascorp [package insert]. Memphis, TN: Accredo Health Group; 2011.