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Antivenin (latrodectus mactans)

Medically reviewed by Last updated on Aug 2, 2022.

Commonly used brand name(s)

In the U.S.

  • Antivenin-Spider

In Canada

  • Antivenin

Available Dosage Forms:

  • Powder for Solution

Therapeutic Class: Antivenom

Uses for antivenin (latrodectus mactans)

Black widow spider antivenin belongs to a group of medicines known as immunizing agents. It is used to treat patients with serious symptoms caused by the bites of the black widow spider.

Antivenin (latrodectus mactans) is to be given only by or under the direct supervision of a doctor.

Before using antivenin (latrodectus mactans)

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For antivenin (latrodectus mactans), the following should be considered:


Tell your doctor if you have ever had any unusual or allergic reaction to antivenin (latrodectus mactans) or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.


Appropriate studies performed to date have not demonstrated pediatric-specific problems that would limit the usefulness of antivenin injection in children.


Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of antivenin injection in the elderly. However, elderly patients are more likely to have unwanted effects from bites from the black widow spider, suggesting that antivenin should be given as a preferred initial therapy .


There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.

Interactions with medicines

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your healthcare professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine.

Interactions with food/tobacco/alcohol

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other medical problems

The presence of other medical problems may affect the use of antivenin (latrodectus mactans). Make sure you tell your doctor if you have any other medical problems, especially:

  • Allergy to horse serum, history of—Should not be used in patients with this condition unless absolutely necessary.
  • Asthma, history of—Use with caution. May make this condition worse.

Proper use of antivenin (latrodectus mactans)

A nurse or other trained health professional will give you antivenin (latrodectus mactans) in a hospital or clinic. Antivenin (latrodectus mactans) is given as a shot into a muscle (thighs) or vein.

A single dose of antivenin (latrodectus mactans) is usually enough for most patients. However, a second dose may be given to some patients if needed.

Precautions while using antivenin (latrodectus mactans)

Your doctor will check your progress closely while you are receiving antivenin (latrodectus mactans). This will allow your doctor to see if the medicine is working properly and to decide if you should continue to receive it.

Antivenin (latrodectus mactans) may cause a serious type of allergic reaction called anaphylaxis. Anaphylaxis requires immediate medical attention. The most serious signs of this reaction are very fast or irregular breathing, gasping for breath, wheezing, or fainting. Other signs may include changes in color of the skin of the face, very fast but irregular heartbeat or pulse, hive-like swellings on the skin, and puffiness or swellings of the eyelids or around the eyes. If these side effects occur, tell your doctor right away.

Check with your doctor right away if you have a feeling of discomfort, fever, inflammation of the joints, itching, muscle aches, rash, or swollen lymph glands within 8 to 12 days after receiving antivenin (latrodectus mactans).

Antivenin (latrodectus mactans) side effects

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur:

Incidence not known

  • Cough
  • difficulty with swallowing
  • dizziness
  • fast heartbeat
  • feeling of discomfort
  • fever
  • hives
  • inflammation of the joints
  • itching
  • muscle aches or cramps
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • reddening of the skin, especially around the ears
  • shortness of breath
  • skin rash
  • swelling of the eyes, face, or inside of the nose
  • swollen lymph glands
  • tightness in the chest
  • unusual tiredness or weakness (sudden and severe)

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

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