Prior to treatment with any product prepared from horse serum, a careful review of the patient's history should be taken emphasizing prior exposure to horse serum or any allergies. Serious sickness and even death could result from the use of horse serum in a sensitive patient. A skin or conjunctival test should be performed prior to administration of Antivenin.
Skin test: Inject into (not under) the skin not more than 0.02 mL of the test material (1:10 dilution of normal horse serum in physiologic saline). Evaluate result in 10 minutes. A positive reaction is an urticarial wheal surrounded by a zone of erythema. A control test using Sodium Chloride Injection facilitates interpretation of the results.
Conjunctival test: For adults instill into the conjunctival sac one drop of a 1:10 dilution of horse serum and for children one drop of 1:100 dilution. Itching of the eye and reddening of the conjunctiva indicate a positive reaction, usually within 10 minutes.
Patients should be observed for serum sickness for an average of 8 to 12 days following administration of Antivenin.
Desensitization should be attempted only when the administration of Antivenin is considered necessary to save life. Epinephrine must be available in case of untoward reaction.
Desensitization: If the history is positive or the results of the sensitivity tests are mildly or quetionably positive, Antivenin should be administered as follows to reduce the risk of an immediate severe allergic reaction:
In separate sterile vials or syringes prepare 1:10 or 1:100 dilutions of Antivenin in Sodium Chloride for Injection.
Allow at least 15 but preferably 30 minutes between injections and only proceed with the next dose if no reactions occurred following the previous dose.
Using a tuberculin syringe, inject subcutaneously 0.1, 0.2 and 0.5 mL of the 1:100 dilution at 15 or 30 minute intervals; 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 sites of injection and administer epinephrine, 1:1000 (0.3 to 1.0 mL subcutaneously, 0.05 to 0.1 mL intravenously), proximal to the tourniquet or into another extremity. Wait at least 30 minutes before giving another injection of Antivenin, the amount of which should be the same as the last one not evoking a reaction.
If no reaction has occurred after 0.5 mL of undiluted Antivenin has been given, it is probably safe to continue the dose at 15 minute intervals until the entire dose has been injected.
Carcinogenesis, Mutagenesis, Impairment of Fertility
No long term studies in animals have been performed to evaluate the potential for carcinogenesis, mutagenesis, or impairment of fertility.
Pregnancy Category C. Animal reproduction studies have not been conducted with Black Widow Spider Antivenin. It is also not known whether Black Widow Spider Antivenin can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Black Widow Spider Antivenin should be given to a pregnant woman only if clearly needed.
It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Black Widow Spider Antivenin is administered to a nursing woman.
Controlled clinical studies for safety and effectiveness in children have not been conducted; however, there have been virtually no adverse effects reported in those children who have received the product.
Reported clinical experience has not identified differences in responses between the elderly and younger patients. Because of the increased risk of complications from envenomation in elderly patients, the standard of care described in the literature suggests that patients older than 60 years of age should be given Antivenin as a preferred initial therapy (see INDICATIONS AND USAGE).