Scorpion antivenin, antivenin Centruroides sculpturatus equine is used to neutralize the toxic effects of Centruroides scorpion. Initiate treatment as soon as possible 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, and vomiting. For patients with mild scorpion stings, treatment may not be needed as symptoms consist mainly of localized pain which usually resolves over hours to days. Scorpion antivenin is a polyvalent antivenin derived from the plasma of horses immunized with Centruroides scorpion venom. Individuals sensitive to horse proteins may experience early or delayed hypersensitivity reactions to this antivenin.
General Administration Information
For storage information, see the specific product information within the How Supplied section.
Route-Specific Administration
Injectable Administration
-Visually inspect parenteral products for particulate matter and discoloration prior to administration whenever solution and container permit. Do not use if the solution is turbid.
Intravenous Administration
Reconstitution:
-Reconstitute each vial with 5 mL of 0.9% Sodium Chloride Injection.
-Mix by continuous gentle swirling.
-If using more than 1 vial, combine the contents of each vial promptly.
-Further dilute the dose to a total volume of 50 mL with 0.9% Sodium Chloride Injection.
-Discard any partially used vials.
Intravenous infusion:
-Infuse dose intravenously over 10 minutes.
-Closely monitor the patient during and up to 60 minutes following the infusion completion.
General adverse events in clinical trials of scorpion antivenin included fever (4.1%), rash (2.7%), pruritus (2%), myalgia (1.6%), fatigue (1.6%), and lethargy (1.1%). Rash and pruritus were also reported with postmarketing use of scorpion antivenin.
Thirty-nine instances of severe adverse events occurred in 34 patients receiving scorpion antivenin in clinical trials and included respiratory distress, aspiration, hypoxia, pneumonia, and ocular inflammation (eye swelling). No patients discontinued treatment or died due to severe adverse events. Other respiratory adverse events occurring in clinical trials included rhinorrhea (1.8%) and cough (1.4%).
Gastrointestinal adverse events occurring in clinical trials of scorpion antivenin included vomiting (4.7%), nausea (2.1%), and diarrhea (1.3%).
Neurological adverse events occurring in clinical trials of scorpion antivenin include headache (1.9%) and ataxia.
Chest tightness and palpitations have been reported with postmarketing use of scorpion antivenin; a causal relationship to the drug has not been established.
Hypersensitivity reactions including anaphylactoid reactions and serum sickness have been reported with the use of equine-derived antivenins. Anaphylactic shock and acute bronchospasm are possible. Observe patients receiving scorpion antivenin carefully for dyspnea, facial or throat edema, or other signs of immediate reactions during administration. A careful patient history should be taken, emphasizing prior exposure to horse serum or any allergies. Serious sickness and death could result from the use of horse serum in a sensitive patient. In clinical trials, 0.5% of patients treated with scorpion antivenin experienced symptoms of serum sickness. Serum sickness may occur in 5 to 12 days following administration, or sooner if the individual is sensitized. Symptoms of serum sickness may include skin lesions, lymphadenopathy (swollen lymph nodes), fever, and arthralgia (joint pain); patients should be advised to report these symptoms after treatment. The symptoms are generally self-limiting, resolving in 1 to 2 weeks; however, symptomatic care may include antihistamines, nonsteroidal anti-inflammatory drugs (NSAIDs), and corticosteroids.
Severe hypersensitivity reactions, including anaphylaxis, may occur following administration of scorpion antivenin. Therefore, the administration of antivenin requires a specialized care setting and the patient should be hospitalized if possible. The product is derived from the blood of healthy horses immunized with venom from Centruroides scorpions; therefore, patients with equine protein hypersensitivity or patients who have received previous therapy with equine antivenom or antitoxin may be at higher risk for anaphylaxis. Patients should be monitored for signs of hypersensitivity reactions and emergency medications such as epinephrine, corticosteroids, and diphenhydramine should be readily available. The infusion should be terminated and emergency medical care instituted if hypersensitivity reactions develop. Patients should also be monitored for delayed allergic reactions (serum sickness). Scorpion antivenin carries a risk of transmitting infection, such as from viruses, due to the equine source of the product.
Scorpion antivenin contains trace amounts of cresol and should be avoided in patients with cresol hypersensitivity; localized reactions and general myalgias have been reported with the use of cresol as an injectable excipient.
It is not known whether scorpion antivenin causes fetal harm when administered during human pregnancy and animal reproduction studies have not been conducted. Administer scorpion antivenin to a pregnant patient only if the benefit clearly outweighs the risk.
It is not known whether scorpion antivenin is excreted in breast milk. Use caution when administering to a lactating patient. Consider the benefits of breast-feeding, the risk of potential infant drug exposure, and the risk of an untreated or inadequately treated condition. If a breast-feeding infant experiences an adverse effect related to a maternally administered drug, healthcare providers are encouraged to report the adverse effect to the FDA.
For the treatment of Centruroides scorpion sting in patients with clinically significant signs of envenomation:
NOTE: Initiate treatment as soon as possible after scorpion sting in patients who develop clinically important signs of 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, and vomiting.
NOTE: Significant envenomation is more likely to occur in young children than in adults. Mild envenomation, which is more common in adults, mainly consists of localized pain and does not require specific treatment.
NOTE: Uncontrolled observational data from use in Mexico and Arizona, and data from a double-blind, placebo-controlled study of critically ill children aged 6 months to 18 years, suggest that use of the antivenin can resolve significant clinical toxicity within 4 hours after treatment.
NOTE: In North America, scorpions whose venom has medical consequences fall within 1 genus, Centruroides. In the United States there is a single neurotoxic species, Centruroides sculpturatus (previously known as C. exilicauda).
Intravenous dosage:
Adults: 3 vials diluted with 0.9% Sodium Chloride Injection to a total volume of 50 mL and administered IV over 10 minutes as an initial dose. If needed, additional doses of 1 vial diluted with 0.9% Sodium Chloride Injection to a total volume of 50 mL and administered IV over 10 minutes may be given at 30- to 60-minute intervals.
Neonates, Infants, Children, and Adolescents: 3 vials diluted with 0.9% Sodium Chloride Injection to a total volume of 50 mL and administered IV over 10 minutes as an initial dose. If needed, additional doses of 1 vial diluted with 0.9% Sodium Chloride Injection to a total volume of 50 mL and administered IV over 10 minutes may be given at 30- to 60-minute intervals.
Maximum Dosage Limits:
-Adults
No maximum dosage information can be definitely assigned at this time.
-Geriatric
No maximum dosage information can be definitely assigned at this time.
-Adolescents
No maximum dosage information can be definitely assigned at this time.
-Children
No maximum dosage information can be definitely assigned at this time.
-Infants
No maximum dosage information can be definitely assigned at this time.
-Neonates
No maximum dosage information can be definitely assigned at this time.
Patients with Hepatic Impairment Dosing
Specific guidelines for dosage adjustments in hepatic impairment are not available; it appears that no dosage adjustments are needed.
Patients with Renal Impairment Dosing
Specific guidelines for dosage adjustments in renal impairment are not available; it appears that no dosage adjustments are needed.
*non-FDA-approved indication
There are no drug interactions associated with Scorpion Antivenin, Antivenin Centruroides sculpturatus Equine products.
The clinical consequences of scorpion envenomation are the result of specific ion channel toxins present in the venom which stimulate action potentials throughout the peripheral nervous system. Scorpion antivenin is composed of venom specific F(ab')2 fragments of immunoglobulin G (IgG). These fragments bind and neutralize the toxins allowing for redistribution away from target tissues and elimination from the body. Scorpion antivenin is standardized for potency in mice in terms of its LD50 neutralizing capacity per mL. Based on this assay system, the reconstituted contents of each vial (5 mL) will neutralize at least 150 LD50 of Centruroides scorpion venom and contain no more than 35 mg of protein.
In clinical trials, 95% to 100% of patients responded to scorpion antivenin with relief of systemic symptoms in less than 4 hours after initiating treatment. Overall, the mean time from start of the antivenin infusion to resolution of clinical symptoms of envenomation was 1.42 hours (range: 0.2 to 20.5 hours). The time was slightly faster in pediatric patients (1.28 +/- 0.8 hours) than in adults (1.91 +/- 1.4 hrs). Administration of sedatives did not affect the time to symptom resolution.
Scorpion antivenin is administered intravenously. Pharmacokinetic data are available from 8 healthy adult volunteers administered an intravenous scorpion antivenin dose of 47.5 mg. Blood samples were collected from these volunteers over 21 days and the pharmacokinetic parameters were estimated by non-compartmental analysis. The results were: volume of distribution at steady-state 13.6 +/- 5.4 L, clearance 83.5 +/- 38.4 mL/hour, and half-life 159 +/- 57 hours.
Affected cytochrome P450 isoenzymes: none
-Route-Specific Pharmacokinetics
Intravenous Route
Following intravenous administration of a 47.5 mg dose of scorpion antivenin to 8 healthy adult volunteers, the systemic drug exposure (AUC) was 706 +/- 352 mcg/mL x hour.