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ANTIVENIN®Clinical Studies (micrurus fulvius)

14 CLINICAL STUDIES

There have been no well-controlled clinical studies of the use of North American Coral Snake Antivenin (Equine) in patients experiencing envenomation by the Eastern Coral Snake, however a retrospective analysis3 has been published of 387 coral snake exposures treated in a healthcare facility in Florida between 1998 and 2010, including 252 patients who were treated with North American Coral Snake Antivenin (Equine). Patients were managed according to different treatment strategies: (a) asymptomatic at ED arrival and treated empirically (n=134); (b) asymptomatic at ED arrival, but treatment withheld until symptoms appeared (n=106; 6 of the 106 received North American Coral Snake Antivenin (Equine) at some point; the remainder were never treated); (c) symptomatic at ED arrival and treated with North American Coral Snake Antivenin (Equine) (n=112); and (d) symptomatic at ED arrival but not treated with North American Coral Snake Antivenin (Equine) (n=35). The average number of vials administered to treated patients was 3.75 (range 1 – 20 vials); the 17 patients who received repeat treatment were administered 8.3 vials, on average. There was no reported usage of foreign antivenom or acetylcholinesterase inhibitors in this case series. The 387 patients were assessed for clinical outcomes, as shown in Table 1. Outcomes codes range from full recovery with no residual effects ("No Effect") to less than full recovery with significant residual effects ("Major"). Empiric treatment of asymptomatic patients resulted in more 'moderate' and 'major' outcomes compared to withholding treatment until symptoms appeared (p<.001), however, the patients were not randomized and selection biases could have affected this result.

Table 1 – Outcome by Treatment Strategy
Treatment Strategy Empiric
(N = 134)
Withhold
(N = 106)
Symptomatic with AV
(N = 112)
Symptomatic without AV
(N = 35)
ADR, adverse drug reaction; AV, antivenom; Avg, average; LOS, length of stay; ICU, intensive care unit.
*
p < 0.01 between empiric and withhold strategies.
Primary outcome
  Endotracheal intubation (%) 3 (2.2) 1 (0.94) 7 (6.25) 0 (0)
Secondary outcomes
  Days intubated Avg. (SD) 5.67 (2.89) 24 (N/A) 8 (6.22) 0 (0)
  ICU admission (%)* 97 (72.39) 49 (46.23) 90 (80.36) 9 (25.71)
  ICU LOS Avg.(SD) 1.5 (1.18) 1.73 (3.28) 2.25 (3.35) 1.3 (0.5)
  Total LOS Avg.(SD) 1.58 (1.56) 1.17 (2.94) 2.47 (3.68) 0.94 (0.85)
  Antivenom ADR (%)* 26 (19.4) 0 (0) 20 (17.86) 0 (0)
Outcome code %*
  No Effect 4.76 29.29 0 0
  Minor 71.43 56.57 34.23 63.64
  Moderate 20.63 13.13 54.05 36.36
  Major 3.17 1.01 11.71 0

Adverse reactions associated with North American Coral Snake Antivenin (Equine) administration were documented in 46 (18.25%) cases. The most common adverse reactions were hives, rash and/or welts (12%); itching (9%); shortness of breath (8%); hypotension (2%) and angioedema (1%). Antihistamines were administered to 46 patients, corticosteroids to 40, and epinephrine to 10 cases to treat these adverse reactions.

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