For Intravenous use only.
Administer Anavip as soon as possible after rattlesnake bite in patients who develop any signs of envenomation (e.g., local injury, coagulation abnormality, or systemic signs of envenomation).
The amount of antivenin required to treat a snake bitten patient is highly variable owing in part to the venom burden, the potency of the venom and the time to health care presentation. Use supportive measures to treat certain manifestations of rattlesnake envenomation, such as pain, swelling, hypotension, and wound infection. Contact the local poison control centers for additional individual treatment advice.
Prior to initiating treatment perform laboratory analyses, including complete blood count, platelet count, PT, PTT, serum fibrinogen level and routine serum chemistries. Repeat testing at regular intervals to gauge response to therapy and anticipate additional dosing.
Initial Dose: 10 vials
The initial dose of Anavip is 10 vials.
Reconstitute the contents of each vial with 10 milliliters (mL) of sterile normal saline. Reconstitution time should be less than one minute when using continuous gentle swirling.
Inspect the solution visually for particulate matter and discoloration prior to administration. The solution is expected to be clear to yellow/green and opalescent. Do not use if otherwise discolored or turbid.
Combine the contents of the reconstituted vials promptly and further dilute to a total volume of 250 mL with sterile normal saline. Fluid volumes may need to be adjusted for very small children or infants. Poison Control Centers are a helpful resource for individual treatment advice.
Infuse intravenously over 60 minutes.
For the first 10 minutes infuse at a 25-50 mL/hour rate, carefully monitoring for any allergic reactions, including an anaphylactic reactions. Discontinue the infusion if any allergic reaction occurs and institute appropriate emergency treatment. Reassess the risk to benefit before continuing the infusion.
If no reactions occur, the infusion rate may be increased to the full 250 mL/hour rate until completion. If there is any allergic reaction at any time, stop the infusion, treat accordingly, and reassess the need to continue Anavip.
Following the completion of infusion, monitor the patient for at least 60 minutes for any allergic reaction and to determine that local signs of envenomation are not progressing (leading edge of local injury not progressing), systemic symptoms are resolved and coagulation parameters have normalized or are trending toward normal.
Discard partially or unused reconstituted and diluted product.
Additional Dosing to Achieve Initial Control
Administer additional 10 vial doses if needed to arrest the progressive symptoms and repeat every hour. There is no known maximum dose.
Repeat above steps for initial dose as many times as needed until local signs of envenomation are not progressing, systemic symptoms are resolved and coagulation parameters have normalized or are trending toward normal.
Prepare as described above for initial dose.
Once initial control has been achieved, observe the patient to determine any need for further dosing, as described below.
Observation and late Dosing
Monitor patients in a health care setting at least 18 hours following initial control of signs and symptoms. Re-emerging symptoms including coagulopathies may be suppressed with additional 4 vial doses of Anavip as needed. Reconstitute each vial with 10 mL of sterile normal saline. Combine and further dilute to a total of 250 mL. Infuse intravenously over 60 minutes.
3 DOSAGE FORMS AND STRENGTHS
Anavip is supplied as a sterile, lyophilized powder. Each vial contains not more than 120 milligrams (mg) total protein and not less than the indicated number of mouse LD50 neutralizing units:
Snake Species Used for Standardization
Minimum Mouse LD50 Units per Vial
5 WARNINGS AND PRECAUTIONS
Anavip may cause allergic reactions.
Patients with known allergies to horse protein are particularly at risk for an anaphylactic reaction. If signs or symptoms of anaphylaxis or hypersensitivity reactions (including urticaria, rash, tightness of the chest, wheezing, hypertension) occur, discontinue immediately and institute appropriate treatment.
Monitor patients with follow-up visits for signs and symptoms of delayed allergic reactions or serum sickness (rash, fever, myalgia, arthralgia, pruritus, urticarial rash) and treat appropriately if necessary.
5.2 Transmissible Infectious Agents
Anavip is made from equine (horse) plasma and may therefore carry a risk of transmitting infectious agents, e.g., viruses.
5.3 Reactions to Cresol
Trace amounts of cresol from the manufacturing process are contained in Anavip. Localized reactions and generalized myalgias have been reported with the use of cresol as an injectable excipient.
6 ADVERSE REACTIONS
The most common adverse reactions observed in more than 2 percent of patients in the clinical trials for Anavip were: pruritus, nausea, rash, arthralgia, peripheral edema, erythema, headache, myalgia, pain in extremity, and vomiting.
6.1 Clinical Trials Experience
Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice.
A total of 86 patients were treated with Anavip, ranging from 2 to 80 years old. The patient population was comprised of 60 males and 26 females. Patients were monitored for signs and symptoms of adverse reactions, including acute hypersensitivity reactions and serum sickness. Follow-up interviews were conducted at 5, 8, 15 and 22 days after treatment to assess symptoms of ongoing venom effect, serum sickness, and any other adverse reactions.
Table 1 shows the adverse reactions occurring in patients across all clinical trials for Anavip. Seventy six percent (65/86) of patients receiving Anavip reported at least one adverse reaction.
Table 1: Incidence of Adverse Events in Clinical Studies of Anavip by Body System
Patients Reporting at Least One Adverse Event
Skin and subcutaneous tissue disorders
Musculoskeletal and connective tissue disorders
Pain in extremity
General disorders and administration site conditions
Nervous system disorders
Metabolism and nutrition disorders
Respiratory, thoracic and mediastinal disorders
Blood and lymphatic system disorders
8 USE IN SPECIFIC POPULATIONS
Pregnancy Category C: Animal reproduction studies have not been conducted with Anavip. It is also not known whether Anavip can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Anavip should be given to a pregnant woman only if clearly needed.
8.3 Nursing Mothers
It is not known whether Anavip is excreted in human breast milk. Because many drugs are excreted in human milk, caution should be exercised when Anavip is administered to a nursing woman.
8.4 Pediatric Use
Twenty-four percent (21/86) of patients studied in clinical trials were 16 years of age or younger (6 patients were 2 years of age to 5 years of age, 15 patients ranged from at least 5 years of age to 16 years of age). None of the pediatric patients in the phase 3 study experienced a recurrent coagulopathic effect. All adverse reactions in the pediatric patients were non-serious. The most frequent adverse reactions among pediatric patients were nausea and vomiting, itching and fever. Thus, the safety and efficacy in the pediatric population was not different from adults.
8.5 Geriatric Use
Over 9 percent (8/86) of patients studied in clinical trials were over 65 years of age. The efficacy of Anavip in the geriatric population appears comparable to the overall population.