Relevance: This will be the first adequately powered study of the ability of atomoxetine to prevent the vasovagal reflex. It will also provide insight as to whether norepinephrine transport inhibition functions here to maintain venous return or increase systemic vascular resistance. If positive, the study will provide a strong biomedical rationale and preliminary clinical results leading to a randomized clinical trial of atomoxetine for the prevention of vasovagal syncope.