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Crofab

Clinical Pharmacology
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Clinical Pharmacology

Crofab

Clinical Studies

No clinical studies have been conducted comparing CroFab with other antivenins, therefore, no comparisons can be made between CroFab and other antivenins.

Two clinical trials using CroFab have been conducted. They were prospectively defined, open-label, multi-center trials conducted in otherwise healthy patients 11 years of age or older who had suffered from minimal or moderate (as defined in Table 3) North American crotalid envenomation that showed evidence of progression. Progression was defined as the worsening of any evaluation parameter used in the grading of an envenomation: local injury, laboratory abnormality or symptoms and signs attributable to crotalid snake venom poisoning. Both clinical trials excluded patients with Copperhead envenomation. To date, there are no clinical data supporting the efficacy of CroFab in patients presenting with severe envenomation.

Table 3. Definition of Minimal, Moderate, and Severe Envenomation in Clinical Studies of CroFab

Envenomation Category

Definition

Minimal

Swelling, pain, and ecchymosis limited to the immediate bite site;

Systemic signs and symptoms absent;

Coagulation parameters normal with no clinical evidence of bleeding.

Moderate

Swelling, pain, and ecchymosis involving less than a full extremity or, if bite was sustained on the trunk,

head or neck, extending less than 50 cm;

Systemic signs and symptoms may be present but not life threatening, including but not limited to nausea,

vomiting, oral paresthesia or unusual tastes, mild hypotension (systolic blood pressure <90 mmHg), mild tachycardia (heart rate <150), and tachypnea;

Coagulation parameters may be abnormal, but no clinical evidence of bleeding present. Minor hematuria, gum bleeding and nosebleeds are allowed if they are not considered severe in the investigator†s judgment.

Severe

Swelling, pain, and ecchymosis involving more than an entire extremity or threatening the airway;

Systemic signs and symptoms are markedly abnormal, including severe alteration of mental status, severe hypotension, severe tachycardia, tachypnea, or respiratory insufficiency;

Coagulation parameters are abnormal, with serious bleeding or severe threat of bleeding.

In both clinical studies, efficacy was determined using a Snakebite Severity Score (SSS) [2] (referred to as the efficacy score or ES in these clinical studies) and an investigator†s clinical assessment (ICA) of efficacy. The SSS (referred to as the ES) is a tool used to measure the severity of envenomation based on six body categories: local wound (e.g., pain, swelling and ecchymosis), pul-monary, cardiovascular, gastrointestinal, hematological, and nervous system effects. A higher score indicates worse symptoms. In a retrospective study using medical records of 108 snakebite victims [2], the SSS has been shown to correlate well with physicians' assessment of the patient's condition at presentation (Pearson correlation coefficient: r=0.63, p<0.0001) and when the patient's condition was at its worst (r=0.70,p<0.0001).In this study, the condition of 87/108 patients worsened during hospital-ization. Changes in the physicians' assessment of condition correlated well with changes in SSS. CroFab was required to prevent an increase in the ES in order to demonstrate efficacy.

Brand Name: Crofab
Generic Name: Crotalidae Polyvalent Immune Fab Ovine
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