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Latrodectus mactans

Generic: Anthracinum, Apis Mellifica, Arnica Montana, Calendula Officinalis, Conium Maculatum, Echinacea (Angustifolia), Euphorbia Pilulifera, Grindelia, Histaminum Hydrochloricum, Hypericum Perforatum, Lachesis Mutus, Latrodectus Mactans, Ledum Palustre, Pyrogenium, Tarentula Cubensis

Verified·Apr 23, 2026
Manufacturer
Merck
NDC
0220-3065
Route
ORAL
ICD-10 indication
T63.311A

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About Latrodectus mactans

What is this medication? Antivenin (Latrodectus mactans) is a specialized antivenin used specifically to treat patients who have been bitten by a black widow spider. This medication is derived from equine serum and contains specific antibodies designed to neutralize the toxins introduced into the human body during a bite. It is generally reserved for individuals experiencing severe systemic symptoms, such as debilitating muscle pain, intense abdominal cramping, or hypertension, that cannot be managed with standard supportive treatments like pain relievers and muscle relaxants. The administration of this medication typically occurs in a clinical or hospital setting via an intravenous or intramuscular injection. By binding to the venom, the antivenin helps to rapidly alleviate the painful muscle spasms and other neurological effects associated with latrodectism. Because it is derived from biological sources, healthcare providers must monitor patients closely during administration for potential allergic reactions or serum sickness.

Copay & patient assistance

Detailed copay and financial assistance information is not publicly available for this medication at this time. Please consult your pharmacist or the manufacturer's official patient support program for more details.

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Prescribing information

From the FDA-approved label for Latrodectus mactans. Official source: DailyMed (NLM) · Label effective Oct 23, 2023

Indications and usage
Rx Only*
Dosage and administration
Adults and children: At the onset of symptoms, dissolve 5 pellets under the tongue 3 times a day until symptoms are relieved or as directed by a doctor.

Label text is reproduced as-is from the FDA-approved label. We do not paraphrase, summarize, or omit. Content above is for informational purposes only and is not medical advice. Always consult your prescribing clinician or pharmacist before making decisions about your medication.

Conditions we've indexed resources for

Click a condition to see copay cards, grants, and PA rules specific to it. For the full list of FDA-approved indications, see Prescribing information above.

Prior authorization & coverage

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Medicare Part D

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How this page is sourced

  • Drug identity verified against openFDA NDC Directory.
  • Label text (when shown) originates from NLM DailyMed.
  • Copay and assistance URLs verified periodically; if you hit a broken link, tell us.