Antivenin (Black Widow Spider) Dosage

Usual Adult Dose for Venomous Spider Bite

2.5 mL (1 vial), IM, once

For severe cases, patients under 12 years, or patients in shock:
2.5 mL, in 10 to 50 mL saline, IV, over 15 minutes, once

Comments:

• Symptoms usually subside in 1 to 3 hours.
• Although one dose is usually adequate, a second dose may be necessary in some cases.
• In otherwise healthy patients between 16 and 60 years, antivenin may be deferred and treatment with muscle relaxants considered.

Usual Pediatric Dose for Venomous Spider Bite

2.5 mL (1 vial), IM, once

For severe cases, patients under 12 years, or patients in shock:
2.5 mL, in 10 to 50 mL saline, IV, over 15 minutes, once

Comments:

• Symptoms usually subside in 1 to 3 hours.
• Although one dose is usually adequate, a second dose may be necessary in some cases.
• In otherwise healthy patients between 16 and 60 years, antivenin may be deferred and treatment with muscle relaxants considered.

Renal Dose Adjustments

Data not available

Liver Dose Adjustments

Data not available

Dose Adjustments

Desensitization should only be considered if antivenin is necessary to save life.

Desensitization (for positive history, or mild to questionable positive test results):

• In separate sterile vials or syringes, prepare 1:10 and 1:100 dilutions of antivenin:sodium chloride for injection.
• Using a tuberculin syringe, inject subcutaneously 0.1, 0.2, and 0.5 mL of 1:100 solution at least 15 (preferably 30) minutes apart; repeat cycle with the 1:10 dilution, and finally undiluted antivenin. Only proceed with the next injection if no reaction occurs.
• If a reaction occurs, place a tourniquet proximal to the injection site and administer epinephrine, 1:1000 (0.3 to 1 mL subcutaneously, or 0.05 to 0.1 mL IV), proximal to the tourniquet or into another extremity. Wait at least 30 minutes before giving more antivenin (in the amount last given that did not evoke a reaction).
• If no reaction after 0.5 mL of undiluted antivenin is administered, it is probably safe to continue the dose at 15 minute intervals until the entire dose has been administered.

Dialysis

Data not available

Other Comments

Administration advice:

• The anterolateral thigh is the preferred IM location, so that a tourniquet may be applied in the case of a systemic reaction.

• Store at 36 to 46F (2 to 8C).
• Do not freeze.

• Reconstitute with 2.5 mL of supplied diluent.
• With the needle still in the stopper, shake the vial to dissolve contents completely.
• When reconstituted, the color ranges from light (straw) to very dark (iced tea); color has no effect on potency.

See also:

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer