Dosing and Administration

Continued Dosing for Complete Control1


CroFab® Dosing and Administration

CroFab® Crotalidae Polyvalent Immune Fab (Ovine) is available as a lyophilized powder. Each vial contains up to 1 gram of total protein, a maximum of 0.03 mg of mercury, and not less than the indicated number of mouse LD50 neutralizing units.

Dosing is based on clinical response


Administer CroFab® to achieve initial envenomation control1

  • Infuse over 60 minutes, proceeding slowly over the first 10 minutes at a 25- to 50-mL/hour rate with careful observation for any allergic reaction
  • If no allergic reaction occurs, increase infusion rate to the full 250 mL/hour until completion


Check for signs of initial control

Signs of initial control include:

  • Halting of the progression of local effects, such as edema and ecchymosis
  • A clear trend toward improvement in coagulation abnormalities, such as thrombocytopenia and spontaneous bleeding
  • Resolution of all systemic effects,* such as nausea, vomiting, dizziness, or tachycardia

*Excluding fasciculations or myokymia, which may be refractory to antivenom.

Continue CroFab® dosing to help prevent recurrent venom effects 1

Maintenance Dose Schedule

  • After initial control is established, an additional 2-vial dose of CroFab® every 6 hours for up to 18 hours (a total of 3 doses) is recommended

In a prospective clinical trial comparing as-needed (PRN) and maintenance dosing schedules:

  • 100% of patients achieved initial control of envenomation
  • A significant decrease (improvement) in mean snakebite severity score was observed across patient groups within 12 hours
  • No patient in the scheduled group received additional CroFab®, while 8 patients (50%) in the PRN group received additional doses for the first 12 hours

Continue CroFab® dosing to help prevent recurrent venom effects1

With any venomous North American pit viper bite, coagulation abnormalities may persist even after initial control of envenomation

  • Significant hypofibrinogenemia and thrombocytopenia lasting up to 2 weeks may occur after envenomation by North American pit vipers
  • 53% of patients with initial control of moderate pit viper envenomation had recurrent, persistent, or late coagulopathy 2 to 14 days later
  • Because fibrinogen and platelet levels change rapidly after CroFab® administration, coagulation studies and platelet counts should be rechecked within 1 hour of CroFab® dosing
  • Patients receiving a regularly scheduled maintenance dose (n=14) experienced a lower incidence of coagulation abnormalities at follow-up compared with patients who were given additional doses based on perceived need (n=16)

Recurrence of coagulopathies at follow-up in scheduled and PRN dosing groups


Study description

Results are from a prospective, open-label, multicenter trial of 31 otherwise healthy patients 10 years of age or older who had suffered from minimal or moderate North American pit viper envenomation that showed evidence of progression. The study compared 2 different dosing schedules. Patients were given an initial intravenous dose of 6 vials of CroFab® with an option to re-treat with an additional 6 vials, if needed, to achieve initial control of the envenomation syndrome. Once initial control was achieved, patients were randomized to receive additional CroFab® either every 6 hours for 18 hours (scheduled group) or as needed (PRN group).

Numbers are expressed as percent of patients who had a follow-up platelet count that was less than the count at hospital discharge, or a fibrinogen level less than 50% of the level at hospital discharge.

Follow-up data not available for 1 patient.

§p=.04 by Fisher exact test.

Selected Safety Information

In clinical trials, recurrent coagulopathy (the return of a coagulation abnormality after it has been successfully treated with antivenin), characterized by decreased fibrinogen, decreased platelets, and elevated prothrombin time, occurred in approximately half of the patients studied. Recurrent coagulopathy may persist for 1 to 2 weeks or more.