Prophylaxis against early anaphylactic reactions to snake antivenom

BMJ 1999;319:920 ( 2 October )

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Prophylaxis against early anaphylactic reactions to snake antivenom

Stopping trials early may result in insufficient evidence being accrued

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Stopping trials early may result in insufficient evidence being accrued

The first 150 words of the full text of this article appear below.

EDITOR $---$ Fan et al's paper is the second in the BMJ recently to investigate prophylaxis against adverse effects of snake antivenom.¹Earlier, Premawardhena et al in Sri Lanka concluded that givinglow dose subcutaneous adrenaline before antivenom could preventacute adverse reactions.² The Brazilian study (by Fan et al)showed no benefit in using promethazine as pretreatment.¹ Perhapsmore interesting than the conclusions, however, is that both theseclinical trials were stopped early because of interim analyses;they provide examples of the use and pitfalls of suchanalyses.

The Sri Lankan group stopped recruitment halfway through its study since the analysis showed a significant reduction in allacute adverse effects when adrenaline was used as pretreatmentrather than placebo (P=0.0002). Unfortunately, in subanalysisof the severity of adverse reactions in the two groups the differencesin incidence of mild, moderate, and severe reactions barely reachedsignificance due to the . . . [Full text of this article]

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Sequential randomised and double blind trial of promethazine prophylaxis against early anaphylactic reactions to antivenom for bothrops snake bites: Hui Wen Fan, Luiz F Marcopito, João Luiz C Cardoso, Francisco O S França, Ceila M S Malaque, Ronnei A Ferrari, Robert David G Theakston, and David A Warrell
BMJ 1999 318: 1451-1452. [Abstract] [Full Text] [PDF]