A sample size of 56 syncope patients would have 85% power to detect a 60% relative risk reduction from a placebo outcome rate of 65%, using an unmatched 2-tailed test with alpha=0.05. To compensate for the report dropout rate we will inflate the sample by 15% to 64 subjects. A formal, blinded mid-way safety and efficacy analysis will be performed with a p<0.01 stopping rule for efficacy. The sample size will be inflated to 74 to account for spending power on the interim analysis. This will provide 85% power to detect an 80% relative risk reduction.