The panel recommends that patients be observed in the hospital for 18 – 24 hours following initial control of the envenomation syndrome, with serial examinations performed approximately every 6 – 8 hours during this interval. The panel recommends that most patients have laboratory studies (protime, hemoglobin, platelet count, and fibrinogen level) measured twice prior to discharge: once 6 – 12 hours after initial control, which appears

to be the time at which the risk of recurrent hematologic venom effects is greatest, and again prior to discharge [25]. Unfavourable trends in protime, Inhibitors,research,lifescience,medical fibrinogen, or platelet counts should prompt additional testing. Because only 5 – 10% of copperhead envenomation victims develop hematologic venom effects at any time, it is reasonable to forego one set of follow-up lab tests in those copperhead victims who have never manifest coagulopathy, thrombocytopenia, or systemic Inhibitors,research,lifescience,medical bleeding [40]. In the current FDA-approved prescribing information, the manufacturer of antivenom recommends administration of additional 2-vial doses of antivenom given 6, 12, and 18 hours after initial Inhibitors,research,lifescience,medical control is achieved [43]. In a randomized WP1066 nmr clinical trial, this practice reduced the proportion of patients with recurrent

local tissue effects from 8/16 (50%) to 0/15 (0%) [11]. However, cases of recurrent local tissue effects developing in maintenance-treated patients

have been reported [26,39,40,47]. The cost-effectiveness Inhibitors,research,lifescience,medical of maintenance therapy is unclear; in a randomized clinical trial, patients randomized to receive maintenance therapy and patients randomized to receive additional antivenom administered as needed to treat recurrent swelling received the same median number of antivenom vials [11]. The extent to which maintenance therapy reduces Inhibitors,research,lifescience,medical the risk of recurrent and delayed-onset hemorrhagic venom effects is not precisely known. Results of the antivenom phase III premarketing trial appeared to show a reduction Cytidine deaminase in the incidence rate of recurrent hematologic venom effects in patients who received maintenance therapy. In that trial, recurrent thrombocytopenia was noted in 2/14 (14%) patients who received maintenance antivenom therapy, compared with 9/16 (56%) patients who did not receive maintenance therapy [43]. In the same study, recurrent hypofibrinogenemia was noted in 2/14 (14%) of patients receiving maintenance therapy and 7/16 (44%) of those who did not receive maintenance. Small sample size and the large proportion of patients in the no-maintenance group who received rescue therapy due to recurrent local tissue effects makes any estimate of the effect of maintenance antivenom therapy difficult to interpret.