IngentaConnect Route of administration of redback spider bite antivenom: Determi...

Abstract:

Objective:

To determine current beliefs of Australasian emergency physicians, to form the basis of `stopping rules' for a clinical trial of intravenous (i.v.) versus intramuscular (i.m.) redback spider antivenom. Methods:

An email survey of fellows and trainees of the Australasian College for Emergency Medicine. Results:

There were 218 responses; 30% used the i.v. route exclusively, 16% used the i.m route exclusively, 17% used i.m. followed by i.v. if there was a poor initial clinical response, and 38% stated that they had no particular preference. The probability given by respondents that the i.v. route is superior allowed us to differentiate `i.v. enthusiasts' from `i.v. sceptics'. Median predicted response rates were 90% versus 80% for the i.v. route and 60% versus 75% for the i.m. route in the enthusiastic and sceptical groups, respectively. The median expected absolute advantage of i.v. compared with i.m. antivenom was 20% versus 5%, respectively. The median number-needed-to-treat threshold that would lead respondents to choose the i.v. route in preference to the i.m. was 5. Conclusion:

Australasian emergency physicians have polarized views on the optimal route for administering redback spider antivenom. We were therefore able to define both sceptical and enthusiastic priors for a fully Bayesian trial analysis. Our findings support using a number needed to treat of 5 (20% absolute advantage) for powering a clinical study and for determining the point at which it should be stopped.

Keywords: administration and dosage; antivenom; black widow spider; envenoming; redback spider

Document Type: Research article

DOI: 10.1111/j.1742-6723.2007.01014.x

Affiliations: 1: Discipline of Clinical Pharmacology, University of Newcastle, Newcastle, New South Wales, Australia

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Route of administration of redback spider bite antivenom: Determining clinician beliefs to facilitate Bayesian analysis of a clinical trial