The main question in the study is whether people taking fludrocortisone are less likely to faint than people taking an inactive pill called a placebo.

Fludrocortisone is a drug that stimulates the body to retain salt and water. The investigators know from some studies that it might prevent people from fainting at home and in the community, while they are carrying on with their lives. There is some evidence that salt and water retention help prevent fainting, but no one has a clear idea about whether this is true. This study will try to determine if that is true.

About 10% of adults faint recurrently. These patients are often highly symptomatic, have problems with employment and driving, and have well-documented reduced quality of life. There are no therapies that have withstood the test of adequately conducted and credible randomized clinical trials.

There is ample evidence of the importance of blood volume in the pathophysiology of vasovagal syncope. Fludrocortisone acetate is a corticosteroid with a mild enhancement of glucocorticoid activity and a marked increase in mineralocorticoid activity. It has no appreciable glucocorticoid effect at doses between 0.05 to 0.2 mg, which are the commonly used clinical doses for various disorders requiring mineralocorticoid adrenal replacement. The acute actions of fludrocortisone acetate are sodium and water retention, at the expense of urinary potassium excretion. Blood volume expansion with either dietary salt supplementation or fludrocortisone is often recommended by clinicians for the treatment of vasovagal syncope despite a paucity of good evidence for their efficacy. Four clinical studies suggest its utility in the prevention of syncope. Fludrocortisone might decrease the incidence of vasovagal syncope, but the quality of the evidence supporting its use is poor. There are no randomized, placebo-controlled trials of fludrocortisone for the prevention of vasovagal syncope. In this 5-year study the investigators will test the hypothesis that fludrocortisone prevents recurrences of vasovagal syncope.

Inclusion Criteria:

• Syncope as a cause of loss of consciousness according to European Society of Cardiology criteria
• > 2 lifetime syncopal spells preceding enrollment
• > or = to -2 points on the Syncope Symptom Score for Structurally Normal Hearts
• Age > 18 years with informed consent, or age > 14 years with consent and informed parental consent

Exclusion Criteria:

• Other causes of syncope, such as ventricular tachycardia, complete heart block, postural (orthostatic) hypotension or hypersensitive carotid sinus syndrome
• An inability to give informed consent
• Important valvular, coronary, myocardial or conduction abnormality or significant arrhythmia
• Hypertrophic cardiomyopathy
• A known intolerance to fludrocortisone
• Another clinical need for fludrocortisone that cannot be met with other drugs
• A permanent pacemaker
• A seizure disorder
• A major chronic non cardiovascular disease
• Hypertension (blood pressure ≥ 130/85 on 2 occasions) or heart failure
• Renal dysfunction (baseline glomerular filtration rate reduced below 60 ml/min/1.73m2 according to the Cockroft-Gault formula)
• Diabetes mellitus
• Hepatic disease
• Glaucoma
• Any prior use of fludrocortisone acetate
• A 5-minute stand test resulting in diagnosis of postural orthostatic tachycardia syndrome or orthostatic hypotension

Median age was 30.5 years and 146 were women.

Adverse event data were collected for the length of each participant's time in the trial up to 1 year.