Latrodectus Mactans

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Latrodectus Mactans uses


Latrodectus Mactans (Latrodectus Mactans) is a sterile, non-pyrogenic preparation derived by drying a frozen solution of specific venom-neutralizing globulins obtained from the blood serum of healthy horses immunized against venom of black widow spiders (Latrodectus Mactans). It is standardized by biological assay on mice, in terms of one dose of Latrodectus Mactans neutralizing the venom in not less than 6000 mouse LD50 of Latrodectus Mactans. Thimerosal (mercury derivative) 1:10,000 is added as a preservative. When constituted as specified, it is opalescent, ranging in color from light (straw) to very dark (iced tea), and contains not more than 20.0 percent of solids.

Each vial contains not less than 6000 Latrodectus Mactans units. One unit of Latrodectus Mactans will neutralize one average mouse lethal dose of black widow spider venom when the Latrodectus Mactans and the venom are injected simultaneously in mice under suitable conditions.


The pharmacological mode of action is unknown and metabolic and pharmacokinetic data in humans are unavailable.


Latrodectus Mactans (Latrodectus Mactans) is used to treat patients with symptoms due to bites by the black widow spider (Latrodectus Mactans). Early use of the Latrodectus Mactans is emphasized for prompt relief.

Local muscular cramps begin from 15 minutes to several hours after the bite which usually produces a sharp pain similar to that caused by puncture with a needle. The exact sequence of symptoms depends somewhat on the location of the bite. The venom acts on the myoneural junctions or on the nerve endings, causing an ascending motor paralysis or destruction of the peripheral nerve endings. The groups of muscles most frequently affected at first are those of the thigh, shoulder, and back. After a varying length of time, the pain becomes more severe, spreading to the abdomen, and weakness and tremor usually develop. The abdominal muscles assume a boardlike rigidity, but tenderness is slight. Respiration is thoracic. The patient is restless and anxious. Feeble pulse, cold, clammy skin, labored breathing and speech, light stupor, and delirium may occur. Convulsions also may occur, particularly in small children. The temperature may be normal or slightly elevated. Urinary retention, shock, cyanosis, nausea and vomiting, insomnia, and cold sweats also have been reported. The syndrome following the bite of the black widow spider may be confused easily with any medical or surgical condition with acute abdominal symptoms.

The symptoms of black widow spider bite increase in severity for several hours, perhaps a day, and then very slowly become less severe, gradually passing off in the course of two or three days except in fatal cases. Residual symptoms such as general weakness, tingling, nervousness, and transient muscle spasm may persist for weeks or months after recovery from the acute stage.

If possible, the patient should be hospitalized. Other additional measures giving greatest relief are prolonged warm baths and intravenous injection of 10 mL of 10 percent solution of calcium gluconate repeated as necessary to control muscle pain. Morphine also may be required to control pain. Barbiturates may be used for extreme restlessness. However, as the venom is a neurotoxin, it can cause respiratory paralysis. This must be borne in mind when considering use of morphine or a barbiturate. Adrenocorticosteroids have been used with varying degrees of success. Supportive therapy is indicated by the condition of the patient. Local treatment of the site of the bite is of no value. Nothing is gained by applying a tourniquet or by attempting to remove venom from the site of the bite by incision and suction.

In otherwise healthy individuals between the ages of 16 and 60, the use of Latrodectus Mactans may be deferred and treatment with muscle relaxants may be considered.



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. Serum 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 Latrodectus Mactans. However, an anaphylactic reaction to Latrodectus Mactans may occur even following a negative skin or conjunctival test.

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 Latrodectus Mactans.

Desensitization should be attempted only when the administration of Latrodectus Mactans 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 questionably positive, Latrodectus Mactans 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 Latrodectus Mactans 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 Latrodectus Mactans.
  • 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 Latrodectus Mactans, 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 Latrodectus Mactans has been given, it is probably safe to continue the dose at 15 minute intervals until the entire dose has been injected.


Patients with Asthma

Anaphylactic reactions and death have been reported in patients with a medical history of asthma.

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 Latrodectus Mactans. It is also not known whether Black Widow Spider Latrodectus Mactans can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Black Widow Spider Latrodectus Mactans should be given to a pregnant woman only if clearly needed.

Nursing Mothers

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 Latrodectus Mactans is administered to a nursing woman.

Pediatric Use

Controlled clinical studies for safety and effectiveness in children have not been conducted.

Geriatric Use

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 Latrodectus Mactans as a preferred initial therapy.



The following adverse reactions have been reported following the use of Latrodectus Mactans: Hypersensitivity reactions including anaphylaxis and serum sickness. Muscle cramps have also been reported.


Using a sterile syringe, inject 2.5 mL of Sterile Water for Injection into the vial of Latrodectus Mactans. With the needle still in the rubber stopper, shake the vial to dissolve the contents completely.

Parenteral drug products should be inspected visually for particulate matter prior to administration, whenever solution and container permit.

The dose for adults and children is the entire contents of a restored vial (2.5 mL) of Latrodectus Mactans. It may be given intramuscularly, preferably in the region of the anterolateral thigh so that a tourniquet may be applied in the event of a systemic reaction. Symptoms usually subside in 1 to 3 hours. Although one dose of Latrodectus Mactans usually is adequate, a second dose may be necessary in some cases.

Latrodectus Mactans also may be given intravenously in 10 to 50 mL of saline solution over a 15 minute period. It is the preferred route in severe cases, or when the patient is under 12, or in shock. One restored vial usually is enough.


No. 5424 - Latrodectus Mactans, equine origin is a white to gray crystalline powder, each vial containing not less than 6000 Latrodectus Mactans units. Thimerosal (mercury derivative) 1:10,000 is added as preservative, NDC 0006-5424-02. A 1 mL vial of normal horse serum (1:10 dilution) for sensitivity testing is also included. Thimerosal (mercury derivative) 1:10,000 is added as preservative.


Latrodectus Mactans must be stored and shipped at 2-8°C (36-46°F). When reconstituted as directed, the color of Latrodectus Mactans ranges from light (straw) to very dark (iced tea), but the color has no effect on potency. Do not freeze.


Barron, W. E.: Spider Bites, J. Med. Ass. Georgia 49: 511-512, Oct. 1960.

Micks, D. W.: Insects and Other Arthropods of Medical Importance in Texas, Tex. Rep. Biol. & Med. 18: 624-635, Winter 1960.

Prince, G. E.: Arachnidism in Children, J. Pediat. 49: 101-108, July 1956.

Russell, F. E.: Injuries by Venomous Animals in the United States, J. Amer. Med. Ass. 177: 903-907, Sept. 30, 1961.

Russell, F. E.: Muscle Relaxants in Black Widow Spider (Latrodectus Mactans) Poisoning, Amer. J. Med. Sci. 243: 159-162, Feb. 1962.

Russell, F. E.: Venom Poisoning, Rational Drug Therap. 5: 5-6, Aug. 1971.

Merck Sharp & Dohme Corp., a subsidiary of

MERCK & CO., INC., Whitehouse Station, NJ 08889, USA

For patent information: www.merck.com/product/patent/home.html

Copyright © 2014 Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc.

All rights reserved.

Revised: 03/2015



Latrodectus Mactans pharmaceutical active ingredients containing related brand and generic drugs:

infoActive ingredient is the part of the drug or medicine which is biologically active. This portion of the drug is responsible for the main action of the drug which is intended to cure or reduce the symptom or disease. The other portions of the drug which are inactive are called excipients; there role is to act as vehicle or binder. In contrast to active ingredient, the inactive ingredient's role is not significant in the cure or treatment of the disease. There can be one or more active ingredients in a drug.

Latrodectus Mactans available forms, composition, doses:

infoForm of the medicine is the form in which the medicine is marketed in the market, for example, a medicine X can be in the form of capsule or the form of chewable tablet or the form of tablet. Sometimes same medicine can be available as injection form. Each medicine cannot be in all forms but can be marketed in 1, 2, or 3 forms which the pharmaceutical company decided based on various background research results.
Composition is the list of ingredients which combinedly form a medicine. Both active ingredients and inactive ingredients form the composition. The active ingredient gives the desired therapeutic effect whereas the inactive ingredient helps in making the medicine stable.
Doses are various strengths of the medicine like 10mg, 20mg, 30mg and so on. Each medicine comes in various doses which is decided by the manufacturer, that is, pharmaceutical company. The dose is decided on the severity of the symptom or disease.

Latrodectus Mactans destination | category:

infoDestination is defined as the organism to which the drug or medicine is targeted. For most of the drugs what we discuss, human is the drug destination.
Drug category can be defined as major classification of the drug. For example, an antihistaminic or an antipyretic or anti anginal or pain killer, anti-inflammatory or so.

Latrodectus Mactans Anatomical Therapeutic Chemical codes:

infoA medicine is classified depending on the organ or system it acts [Anatomical], based on what result it gives on what disease, symptom [Therapeutical], based on chemical composition [Chemical]. It is called as ATC code. The code is based on Active ingredients of the medicine. A medicine can have different codes as sometimes it acts on different organs for different indications. Same way, different brands with same active ingredients and same indications can have same ATC code.

Latrodectus Mactans pharmaceutical companies:

infoPharmaceutical companies are drug manufacturing companies that help in complete development of the drug from the background research to formation, clinical trials, release of the drug into the market and marketing of the drug.
Researchers are the persons who are responsible for the scientific research and is responsible for all the background clinical trials that resulted in the development of the drug.



  1. Dailymed."ANTIVENIN (LATRODECTUS MACTANS) KIT [MERCK SHARP & DOHME CORP.]". https://dailymed.nlm.nih.gov/dailym... (accessed August 28, 2018).

Frequently asked Questions

Can i drive or operate heavy machine after consuming Latrodectus Mactans?

Depending on the reaction of the Latrodectus Mactans after taken, if you are feeling dizziness, drowsiness or any weakness as a reaction on your body, Then consider Latrodectus Mactans not safe to drive or operate heavy machine after consumption. Meaning that, do not drive or operate heavy duty machines after taking the capsule if the capsule has a strange reaction on your body like dizziness, drowsiness. As prescribed by a pharmacist, it is dangerous to take alcohol while taking medicines as it exposed patients to drowsiness and health risk. Please take note of such effect most especially when taking Primosa capsule. It's advisable to consult your doctor on time for a proper recommendation and medical consultations.

Is Latrodectus Mactans addictive or habit forming?

Medicines are not designed with the mind of creating an addiction or abuse on the health of the users. Addictive Medicine is categorically called Controlled substances by the government. For instance, Schedule H or X in India and schedule II-V in the US are controlled substances.

Please consult the medicine instruction manual on how to use and ensure it is not a controlled substance.In conclusion, self medication is a killer to your health. Consult your doctor for a proper prescription, recommendation, and guidiance.



sDrugs.com conducted a study on Latrodectus Mactans, and the result of the survey is set out below. It is noteworthy that the product of the survey is based on the perception and impressions of the visitors of the website as well as the views of Latrodectus Mactans consumers. We, as a result of this, advice that you do not base your therapeutic or medical decisions on this result, but rather consult your certified medical experts for their recommendations.

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The information was verified by Dr. Arunabha Ray, MD Pharmacology

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