Taking midodrine can reduce vasovagal syncope in younger healthy patients, according to a new study.
Vasovagal syncope is the most common cause of fainting and is often triggered by dehydration and upright posture, according to Johns Hopkins Medicine. But it can also be caused by stimuli like the sight of blood or sudden emotional distress. The stimulus causes the heart rate and blood pressure to drop rapidly, according to the Mayo Clinic.
The randomized, placebo-controlled, double-blind trial included 133 patients with recurrent vasovagal syncope and was published in Annals of Internal Medicine. Those that received midodrine were less likely to have one syncope episode (28 of 66 [42%]), compared with those that took the placebo (41 of 67 [61%]). The absolute risk reduction for vasovagal syncope was 19 percentage points (95% confidence interval, 2-36 percentage points).
The study included patients from 25 university hospitals in Canada, the United States, Mexico, and the United Kingdom, who were followed for 12 months. The trial participants were highly symptomatic for vasovagal syncope, having experienced a median of 23 episodes in their lifetime and 5 syncope episodes in the last year, and they had no comorbid conditions.
“We don’t have many arrows in our quiver,” said Robert Sheldon, MD, PhD, a cardiologist at University of Calgary (Alta.) and lead author of the study, referring to the lack of evidence-based treatments for syncope.
For 20 years Sheldon’s lab has been testing drugs that showed some potential. While a previous study of fludrocortisone (Florinef ) showed some benefit, “[midodrine] was the first to be unequivocally, slam-dunk positive,” he said in an interview.
Earlier Trials of Midodrine
Other studies have shown midodrine to prevent syncope on tilt tests. There have been two randomized trials where midodrine significantly reduced vasovagal syncope, but one of these was short and in children, and the other one was open label with no placebo control.
“Risk reduction was very high in previous studies,” Sheldon said in an interview. But, because they were open label, there was a huge placebo effect, he noted.
“There were no adequately done, adequately powered [studies] that have been positive,” Sheldon added.
New Study Methods and Outcomes
The study published in Annals of Internal Medicine this week included patients over 18 years of age with a Calgary Syncope Symptom Score of at least 2. All were educated on lifestyle measures that can prevent syncopes before beginning to take 5 mg of study drug or placebo three times daily, 4 hours apart.
In these cases, the study authors wrote, “taking medication three times a day seems worth the effort.” But in patients with a lower frequency of episodes, midodrine might not have an adequate payoff.
These results are “impressive,” said Roopinder K. Sandhu, MD, MPH, clinical electrophysiologist at Cedar-Sinai in Los Angeles. “This study demonstrated that midodrine is the first medical therapy, in addition to education and lifestyle measures, to unequivocally pass the scrutiny of an international, placebo-controlled, RCT to show a significant reduction in syncope recurrence in a younger population with frequent syncope events.”