title: Rationale for the prevention of syncope trial IV: assessment of midodrine.
abstract: BACKGROUND
  Vasovagal syncope is a common problem associated with a poor quality of life, which improves when the frequency of syncope is reduced. Effective pharmacological therapies for vasovagal syncope have been elusive. Midodrine is a pro-drug whose primary metabolite is an alpha-1 adrenoreceptor agonist. A few studies have suggested that it may be beneficial in syncope, but all have had significant methodological limitations. A placebo-controlled clinical trial of midodrine for the prevention of vasovagal syncope is needed.
  
  
  METHODS
  The prevention of syncope trial IV (POST 4) is a multicenter, international, randomized, placebo-controlled study of midodrine in the prevention of vasovagal syncope. The primary end point is the time to first recurrence of syncope. Patients will be randomized 1:1 to receive midodrine 10-30 mg/day or matching placebo, and followed for 1 year. Secondary end points include syncope frequency, presyncope, and quality of life. Primary analysis will be performed with an intention-to-treat approach, with a secondary on-treatment analysis.
  A total sample size of 112, split equally between the two groups, achieves 85 % power to detect a 50 % relative risk reduction when the event rates are 55 and 27.5 % in the placebo and midodrine arms. Allowing for 20 % dropout, we propose to enroll 140 patients.
  
  
  BACKGROUND
  POST 4 is registered with                      http://www.clinicaltrials.gov                                         (NCT01456481).
  
  
  CONCLUSIONS
  This study will be the first adequately powered trial to determine whether midodrine is effective in preventing vasovagal syncope. If it is effective, then midodrine may become the first-line pharmacological therapy for this condition.
authors.affiliation: Division of Clinical Pharmacology, Departments of Medicine and Pharmacology, Vanderbilt University, Nashville, TN 37232-2195, USA. satish.raj@vanderbilt.edu
authors.forename: Satish R
authors.initials: SR
authors.lastname: Raj
authors.forename: Peter D
authors.initials: PD
authors.lastname: Faris
authors.forename: Maureen
authors.initials: M
authors.lastname: McRae
authors.forename: Robert S
authors.initials: RS
authors.lastname: Sheldon
mesh_terms: D058646:Adrenergic alpha-1 Receptor Agonists / Q000627:therapeutic use*; D006801:Humans; D057194:Intention to Treat Analysis; D008879:Midodrine / Q000627:therapeutic use*; D015337:Multicenter Studies as Topic; D011446:Prospective Studies; D016032:Randomized Controlled Trials as Topic / Q000379:methods*; D012107:Research Design; D019462:Syncope, Vasovagal / Q000188:drug therapy / Q000517:prevention & control*; D016896:Treatment Outcome
chemical_list: D058646:Adrenergic alpha-1 Receptor Agonists; D008879:Midodrine