1 What is Anavip?

Brand: Anavip

Generic: Crotalidae Immune F(Ab)2 (Equine) (Intravenous Route)

Crotalidae (pit viper) Immune F(Ab)2 (Equine) injection is indicated and intended for management of coagulopathy in patients with North American pit viper envenomation. Indeed, this medicine is designated as an orphan drug by the Food and Drug Administration (FDA or USFDA) for the treatment of poisoning caused by the bite of North American rattlesnake, possibly eliminating the necessity of treatment in an intensive care unit.

This antivenom is preferably used to treat North American pit viper stings as it causes resolution of envenomation symptoms like

  • loss of muscle control,
  • slurred speech,
  • troubled breathing,
  • abnormal eye movements,
  • excessive salivation,
  • frothing at the mouth
  • vomiting.

This medicine is recommended to be given only by or under the direct supervision of a healthcare professional. This product is available in lyophilized powder form which is later used to make an injectable suspension at the time of administration.

2 What to Know Before Using

This medicine is prepared from equine (horse) blood and there is increased risk of serious hypersensitivity reactions. In addition, certain infectious agents including viruses may transmit through horse blood products to the people who have received them.

Although the risk transmission of viruses has been greatly diminished in recent years because of several processes in manufacturing system, you should talk with your doctor about this concern. If you are about to start this drug therapy, the risk-benefit ratio should be considered carefully. This is a decision that your doctor will make with your active participation.

Sometimes the presence of other health disorders affects the beneficial effects of this medicine and even may cause serious toxic effects.

If you have had any allergic reactions to any medicine, you must inform your doctor about that.

In addition, make sure you mention your doctor if you have had hypersensitivity to horse blood products and/or cresol.

Further, this antivenom may cause serious types of allergic reactions, including anaphylaxis.

Anaphylaxis can be life-threatening and requires immediate medical attention. For this reason, you should consult with your doctor immediately if you have developed

  • rashes,
  • itching,
  • hoarseness of voice,
  • respiratory distress,
  • difficulty in swallowing,
  • edema while you are undergoing this antivenom therapy.

However, studies performed with such medications in pregnant and lactating women have failed to demonstrate a risk to the fetus and the nursing baby respectively. Thus, this medicine can be used during pregnancy and lactation if clearly needed.

3 Proper Usage

The treatment should be initiated with this drug immediately after being envenomed by the bite of North American vipers.

This medicine is intended for intravenous use only. It should be given to the patients by a nurse or other trained health professional in a hospital. The therapeutic dose and the duration of drug therapy may vary with the severity of the patient’s condition.

Usual dosing regimen for North American rattlesnake bite consists of 10 vials. Each vial contains 25.2-56.8 mg of sodium chloride, 18.2-85.8 mg of sucrose, and 16.2-51.8 mg of glycine as stabilizers and trace amounts of pepsin, sulfates (<1.7 mg/vial), borates (<1 mg/vial), and cresol (< 0.99 mg/vial).

4 Precautions to Take

Firstly, regular visits to your doctor are recommended to check that this medicine is working properly or not.

In addition, the following guidelines should be followed while you are using such medications:

  • Severe hypersensitivity reactions, including anaphylaxis, may occur with such antivenom therapy. Close patient monitoring for hypersensitivity reactions and readiness with intravenous therapy using epinephrine, corticosteroids, and diphenhydramine hydrochloride is recommended while you are receiving this infusion.
  • If an anaphylactic reaction occurs during the infusion, you should discontinue the antivenom infusion and initiate proper emergency healthcare. Patients with known allergies to horse protein are particularly at risk for an anaphylactic reaction.
  • In addition, you should contact your physician immediately if you experience any unusual bruising or bleeding (e.g. appearance of blood in stools or urine, excessive menstrual bleeding, excessive bruising or persistent oozing from superficial injuries, etc.) after hospital discharge.
  • Moreover, delayed hypersensitivity or serum sickness reactions may also occur after hospital discharge. Thus, you should check for manifestations (e.g. persistent urticaria, arthralgia, myalgia, vomiting, syncope, and angioedema) of delayed allergic reactions or serum sickness. Treatment of such reactions is generally symptomatic including antihistamines, analgesics, antipyretics, and corticosteroids.

5 Potential Side Effects

There are some unwanted side-effects associated with each drug that usually do not need medical attention.

The most common adverse reactions observed in the clinical studies with this antivenom include:

  • nausea,
  • vomiting,
  • pyrexia,
  • rash,
  • pruritus,
  • arthralgia,
  • peripheral edema,
  • myalgia,
  • headache,
  • pain in extremity
  • erythema.

These side-effects usually go away during the treatment episode as your body adjusts to the medicine. Your healthcare professional may advise you about the ways how to prevent or reduce those unwanted side-effects.

Sometimes you may need to consult with the doctor if you feel any of the following toxic effects: