Black widow spider antivenin (Latrodectus mactans antivenin) is used to neutralize the toxic effects of black widow spider bites. The antivenin is derived from the serum of healthy horses immunized against black widow spider venom; thus, use of the antivenin in patients sensitivity to horse serum could result in the development of serum sickness or death. Before starting treatment, carefully review the patient's medical history, emphasizing prior exposure to horse serum or any allergies. Additionally, perform skin or conjunctival sensitivity testing in all patients prior to administration of the dose. After administration of the antivenin, observe patients for serum sickness for an average of 8 to 12 days. The venom of a black widow spider is a neurotoxin that causes systemic symptoms such as severe pain, muscle cramps, abdominal pain, back pain, and hypertension. Envenomation is associated with low mortality. In most cases, symptoms increase in severity for several hours to a day, and then slowly become less severe, subsiding in about 2 days; residual symptoms (e.g., weakness, transient muscle spasm, tingling) may persist for weeks to months. In patients who receive the black widow antivenin, recovery is rapid. Due to the possibility of hypersensitivity reactions, use of the antivenin may be deferred in otherwise healthy patients between the ages of 16 and 60. Treatment of otherwise healthy patients is usually symptomatic with analgesics, muscle relaxants, and intravenous calcium gluconate.
General Administration Information
For storage information, see product information within the How Supplied section.
NOTE: Perform skin or conjunctival sensitivity testing in all patients prior to administration of the antivenin. A 1 mL single-dose vial of normal horse serum (1:10 dilution) is supplied for sensitivity testing.
NOTE: Ensure appropriate medications and equipment to treat anaphylaxis are available. Observe patients for serum sickness for an average of 8 to 12 days after administraiton of the antivenin.
Route-Specific Administration
Injectable Administration
-Administer the antivenin intramuscularly or intravenously.
-Visually inspect parenteral products for particulate matter and discoloration prior to administration whenever solution and container permit. The color of the reconstituted antivenin ranges from light (straw) to very dark (iced tea); color has no effect on potency.
Intravenous Administration
-Intravenous route of administration is preferred for children younger than 12 years old or in any person with severe envenomation or shock.
-Using a sterile syringe, inject 2.5 mL of Sterile Water for Injection into the single-dose vial of antivenin. With the needle still in the rubber stopper, shake the vial to completely dissolve the contents.
-Dilute the reconstituted solution in 10 to 50 mL of 0.9% Sodium Chloride for Injection.
-Administer intravenously over 15 minutes.
Intramuscular Administration
-Using a sterile syringe, inject 2.5 mL of Sterile Water for Injection into the single-dose vial of antivenin. With the needle still in the rubber stopper, shake the vial to completely dissolve the contents.
-Inject entire contents of the vial intramuscularly in the anterolateral thigh so that a tourniquet can be applied if a systemic reaction occurs.
Subcutaneous Administration
-Subcutaneous administration is for desensitization purposes only.
Other Injectable Administration
Intradermal Administration
-Intradermal administration is for sensitivity testing only prior to administration of the antivenin, using the provided normal horse serum.
Ophthalmic Administration
Conjunctival Administration
-Conjunctival administration is for sensitivity testing only prior to administration of the antivenin; using the provided normal diluted horse serum.
Hypersensitivity reactions, including anaphylactoid reactions and serum sickness, have been reported with use of the black widow spider antivenin. Two deaths have been attributed to anaphylactic shock resulting from treatment with the antivenin. The first death occurred following administration of an undiluted bolus dose to a patient with a history of asthma and multiple medication allergies. Shortly after the antivenin was administered, the patient developed respiratory arrest with severe anaphylactic bronchospasm that was refractory to epinephrine and other resuscitative measures. The other antivenin-associated death occurred in a patient with a history of asthma who received an infusion of 2.5 mL of antivenin in 50 mL of 0.9% Sodium Chloride Injection. The patient had previously undergone and displayed no reaction to a subcutaneous test dose of normal horse serum in saline; however, 5 minutes after starting the antivenin infusion (10% infused), the patient developed anxiety, facial tingling, shortness of breath, sinus tachycardia (135 beats/minute), tachypnea (36 breaths/minute), and decreased oxygen saturation on room air (89%). The infusion was stopped, but cardiac arrest occurred within 3 minutes. Other immediate adverse reactions reported after treatment with the antivenin have been skin eruptions that may include urticaria and erythema. Observe patients 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. Serum sickness may occur in 8 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); advise patients 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. Perform skin or conjunctival sensitivity testing prior to administration of the black widow spider antivenin. Ensure epinephrine is at the patients bedside when the antivenin is administered.
Muscle cramps have been reported with the administration of black widow spider antivenin.
Hypersensitivity reactions, including anaphylaxis, serum sickness, and death, have been reported with use of the black widow spider antivenin. Therefore, administration of the antivenin requires a specialized care setting and the patient should be hospitalized if possible. Avoid use of the black widow spider antivenin (which is obtained from the serum of horses) in patients with known equine protein hypersensitivity; serum sickness and death could result from use of horse serum in sensitive patients. However, for severe and life-threatening complications from a black widow spider bite, the antivenin may be administered to patients with equine protein hypersensitivity if used in accordance with the desensitization protocol. Ensure epinephrine is at the bedside when the antivenin is administered. For asthmatic patients, the black widow antivenin must be used with caution. There have been 2 deaths attributed to anaphylactic shock resulting from treatment with the antivenin; in both cases, the patient had a medical history of asthma.
No adequate and well-controlled studies have been conducted regarding use of the black widow spider antivenin in pregnant patients, and the potential of the antivenin to cause fetal harm or affect reproductive capacity is unknown. Effects of the antivenin on labor and delivery are also unknown. Administer during pregnancy only if clearly needed.
Data are limited regarding use of the black widow spider antivenin during breast-feeding, and the excretion of the antivenin in human breast milk is unknown. The manufacturer advises caution when administering to a nursing 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.
Controlled clinical studies for the safety and effectiveness of black widow spider antivenin have not been conducted in children, infants, or neonates; however, use is approved for children under emergent conditions similar to adults. Standards of care described in the medical literature support antivenin use in children and infants with or at risk of serious envenomation. Neonatal exposure to a bite is extremely rare since the most common envenomations occur when disturbing a web structure.
Geriatric patients have an increased risk of complications from envenomation; therefore, the standard of care described in the medical literature suggests the black widow spider antivenin should be administered as the preferred initial therapy in patients older than 60 years of age.
For the treatment of black widow spider bites (Latrodectus mactans) in patients with symptoms:
NOTE: Symptoms of black widow spider bite increase in severity for several hours, perhaps days, and then slowly become less severe except in fatal cases. Early use of the antivenin is emphasized for prompt relief.
NOTE: Hospitalize patients if possible and administer supportive therapy (e.g., calcium gluconate, warm baths, morphine, barbiturates, corticosteroids) as indicated by the condition of the patient. In otherwise healthy patients ages 16 to 60 years, use of the antivenin may be deferred and treatment with muscle relaxants may be considered. Applying a tourniquet or attempting to remove the venom by incision and suction provides no clinical benefit.
NOTE: Perform skin or conjunctival sensitivity testing in all patients prior to administration of the antivenin, as serum sickness and death could occur in patients allergic to horse serum. Observe patients for serum sickness for an average of 8 to 12 days following administration of antivenin.
-for sensitivity testing prior to antivenin administration:
Intradermal dosage (for sensitivity testing):
Adults: 0.02 mL or less of the test material (1:10 dilution of normal horse serum in 0.9% Sodium Chloride) injected intradermally (not under the skin). Evaluate site in 10 minutes. A positive reaction is an urticarial wheal surrounded by erythema. Administer a control test of 0.9% Sodium Chloride Injection to aid in interpretation.
Children and Adolescents: 0.02 mL or less of the test material (1:10 dilution of normal horse serum in 0.9% Sodium Chloride) injected intradermally (not under the skin). Evaluate site in 10 minutes. A positive reaction is an urticarial wheal surrounded by erythema. Administer a control test of 0.9% Sodium Chloride Injection to aid in interpretation.
Conjunctival dosage (for sensitivity testing):
Adults: 1 drop of a 1:10 dilution of normal horse serum in 0.9% Sodium Chloride instilled into the conjunctival sac. Itching of the eye and reddening of the conjunctiva indicate a positive reaction, usually within 10 minutes.
Children and Adolescents: 1 drop of a 1:100 dilution of normal horse serum in 0.9% Sodium Chloride instilled into the conjunctival sac. Itching of the eye and reddening of the conjunctiva indicate a positive reaction, usually within 10 minutes.
-for desensitization prior to administration of antivenin should allergy history be positive or if sensitivity tests are mildly or questionably positive:
NOTE: Attempt desensitization only when administration of the antivenin is considered a life-saving necessity. Ensure epinephrine is available in case of an untoward reaction.
Subcutaneous dosage (desensitization):
Adults: In separate sterile vials or syringes prepare 1:10 or 1:100 dilutions of antivenin in 0.9% Sodium Chloride for Injection. Using a tuberculin syringe, subcutaneously inject 0.1 mL, 0.2 mL, and 0.5 mL of the 1:100 dilution every 30 minutes (should wait a minimum of 15 minutes between doses). Proceed with the next dose only if no reaction occurs with the previous dose. Repeat with the 1:10 dilution, and finally the undiluted antivenin. If there is a reaction after any of the injections, place a tourniquet proximal to the injection sites and administer epinephrine, 1:1000 (0.3 to 1 mL subcutaneous or 0.05 to 0.1 mL IV) proximal to the tourniquet or into another extremity. Wait at least 30 minutes before giving another injection of the antivenin, the amount of which should be the same as the last one not evoking a reaction. If no reaction occurs after giving 0.5 mL of the undiluted antivenin, it is probably safe to continue the dose at 15-minute intervals until the entire dose has been given.
Children and Adolescents: In separate sterile vials or syringes prepare 1:10 or 1:100 dilutions of antivenin in 0.9% Sodium Chloride for Injection. Using a tuberculin syringe, subcutaneously inject 0.1 mL, 0.2 mL, and 0.5 mL of the 1:100 dilution every 30 minutes (should wait a minimum of 15 minutes between doses). Proceed with the next dose only if no reaction occurs with the previous dose. Repeat with the 1:10 dilution, and finally the undiluted antivenin. If there is a reaction after any of the injections, place a tourniquet proximal to the injection sites and administer epinephrine, 1:1000 (0.3 to 1 mL subcutaneous or 0.05 to 0.1 mL IV) proximal to the tourniquet or into another extremity. Wait at least 30 minutes before giving another injection of the antivenin, the amount of which should be the same as the last one not evoking a reaction. If no reaction occurs after giving 0.5 mL of the undiluted antivenin, it is probably safe to continue the dose at 15-minute intervals until the entire dose has been given.
-for the treatment of black widow spider bites with antivenin following sensitivity testing:
Intramuscular dosage:
Adults: 1 vial (2.5 mL) injected intramuscularly in the anterolateral thigh so that a tourniquet can be applied if a systemic reaction occurs. Symptoms usually subside within 1 to 3 hours. Although one dose is usually adequate, a second dose may be necessary.
Children 12 years and older and Adolescents: 1 vial (2.5 mL) injected intramuscularly in the anterolateral thigh so that a tourniquet can be applied if a systemic reaction occurs. Symptoms usually subside within 1 to 3 hours. Although one dose is usually adequate, a second dose may be necessary.
Children younger than 12 years: Intravenous dosing is recommended in children younger than 12 years.
Intravenous dosage:
The intravenous route is preferred when a child is younger than 12 years, or for any person with severe envenomation or shock.
Adults: 1 vial (2.5 mL) in 10 to 50 mL of 0.9% Sodium Chloride Injection given intravenously over 15 minutes. One vial is usually sufficient; however, a second dose may be necessary.
Children and Adolescents: 1 vial (2.5 mL) in 10 to 50 mL of 0.9% Sodium Chloride Injection given intravenously over 15 minutes. One vial is usually sufficient; however, a second dose may be necessary.
Maximum Dosage Limits:
-Adults
2 reconstituted vials (5 mL) IM or IV; although, 1 vial (2.5 mL) is usually adequate for treatment of most cases.
-Geriatric
2 reconstituted vials (5 mL) IM or IV; although, 1 vial (2.5 mL) is usually adequate for treatment of most cases.
-Adolescents
2 reconstituted vials (5 mL) IM or IV; although, 1 vial (2.5 mL) is usually adequate for treatment of most cases.
-Children
12 years: 2 reconstituted vials (5 mL) IM or IV; although, 1 vial (2.5 mL) is usually adequate for treatment of most cases.
1 to 11 years: 2 reconstituted vials (5 mL) IV; although, 1 vial (2.5 mL) is usually adequate for treatment of most cases.
-Infants
Safety and efficacy have not been established.
-Neonates
Safety and efficacy have not been established.
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 Black Widow Spider Antivenin products.
The neurotoxic venom (alpha-latroxin) is likely responsible for the signs and symptoms of black widow spider bites and is thought to exert its activity through calcium-mediated release of neurotransmitters from nerve terminals. Local muscle cramps begin from 15 minutes to several hours after the bite. Muscles most frequently affected first are those of the thigh, shoulder, and back. The pain becomes more severe and intractable, spreading to the abdomen, followed by weakness and tremor. Respirations become thoracic, and the patient is restless and anxious. Other symptoms include urinary retention, nausea and vomiting, light stupor, insomnia, labored speech, delirium, feeble pulse, cold and clammy skin, cold sweats, cyanosis, and shock. Small children may experience convulsions. Temperature may be normal or elevated. Envenomation is associated with low mortality. In most cases, symptoms increase in severity for several hours to a day, and then slowly become less severe, subsiding in about 2 days; residual symptoms (e.g., weakness, transient muscle spasm, tingling) may persist for weeks to months. In patients who receive the black widow antivenin, recovery is rapid. The proposed mechanism of the antivenin is binding of antivenin antibodies to venom toxic constituents.
Black widow spider antivenin is administered intravenously or intramuscularly. Pharmacokinetic data for black widow spider antivenin are unavailable.
Affected cytochrome P450 isoenzymes: none