Clinically Proven to Help Halt Progression of North American Pit Viper Envenomation

CroFab® Crotalidae Polyvalent Immune Fab (Ovine) is a sterile, purified, ovine-derived, polyclonal Fab product. It works by binding to and neutralizing venom toxins, facilitating their redistribution away from target tissues and their elimination from the body.

CroFab® demonstrated efficacy on 2 clinical measures:

Study Description

Results are from a prospective, open-label, multicenter trial of 11 otherwise healthy patients 11 years of age or older who had suffered from minimal or moderate North American pit viper envenomation that showed evidence of progression. Patients received an intravenous dose of 4 vials of CroFab® over 60 minutes. An additional 4-vial dose was administered after completion of the first CroFab® infusion if deemed necessary by the investigator. Efficacy was determined using a snakebite severity score (SSS)* and an investigator's clinical assessment (ICA) of efficacy.

Selected Safety Information

The most common adverse events reported in clinical studies were mild or moderate reactions involving the skin and appendages (primarily urticaria, rash, or pruritus), which occurred in 14 out of 42 patients. Three patients experienced a serious adverse event. Two patients had a severe allergic reaction (severe hives and a severe rash and pruritus) following treatment. One patient had a recurrent coagulopathy due to envenomation, which required rehospitalization and additional antivenin administration.

*The SSS is a validated, objective tool for the clinical evaluation of North American pit viper snakebite in adults. The total score reflects patient evaluation on 6 dimensions: pulmonary system, cardiovascular system, local wound, gastrointestinal system, hematologic symptoms, and central nervous system. The higher the total score, the more severe the snakebite.

The ICA was based on whether the patient had a:

  • Clinical response (pretreatment signs and symptoms of envenomation were arrested or improved after treatment)
  • Partial response (signs and symptoms of envenomation worsened, but at a slower rate than expected after treatment)
  • Nonresponse (the patient's condition was not favorably affected by the treatment)

CroFab® demonstrated efficacy regardless of envenomation severity

CroFab® delivers initial control of envenomation for all severities.

Study Description

Results are from a postmarketing, multicenter, retrospective chart review of snakebite patients (N=209) treated with CroFab® that compared treatment and outcomes of severe envenomation with those of mild and moderate envenomations. The primary efficacy variable was severity of envenomation as determined by a 7-point severity score. Patients were classified as having mild, moderate, or severe envenomation based on their scores just prior to receiving antivenom.

  • 100% (28/28) of patients with severe envenomation had improved severity scores
    - Improvement was seen in all venom effects studied, including limb pain and swelling; cardiovascular, respiratory, gastrointestinal, and neurologic effects; as well as coagulopathy/defibrination syndrome, thrombocytopenia, and significant/spontaneous bleeding

Warnings and Precautions

Patients who experience coagulopathy due to snakebite should be monitored for recurrent coagulopathy for up to 1 week or longer.

Anaphylaxis and hypersensitivity reactions can occur and patients should be monitored closely during treatment. Patients with allergies to papain, chymopapain, other papaya extracts, or the pineapple enzyme bromelain may also be at risk for an allergic reaction to CroFab®. CroFab® contains mercury in the form of ethyl mercury from thimerosal. The final product contains up to 30 mcg or approximately 0.03 mg of mercury per vial, which amounts to no more than 0.6 mg of mercury per dose (based on the maximum dose of 18 vials studied in clinical trials of CroFab®).


CroFab® should not be administered to patients with a known history of hypersensitivity to papaya or papain unless the benefits outweigh the risks and appropriate management for anaphylactic reactions is readily available.