Midodrine Reduces Fainting

Donavyn Coffey

August 04, 2021

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."

"[Taking midodrine] doesn't carry the long-term consequence of pacemakers," she added.

Study Limitations

Limitations of the new study include its small size and short observation period, the authors wrote. Additionally, a large proportion of patients enrolled were also from a single center in Calgary that specializes in syncope care. Twenty-seven patients in the trial stopped taking their assigned medication during the year observation period, but the authors concluded these participants "likely would bias the results against midodrine."

For doctors considering midodrine for their patients, it's critical to confirm the diagnosis and to try patient education first, Sheldon advised.

Lifestyle factors like hydration, adequate sodium intake, and squatting or lying down when the syncope is coming on can sufficiently suppress syncopes in two-thirds of patients, he noted.

This is a treatment for young people, Sandhu said. The median age in the trial was 35, so patients taking midodrine should be younger than 50. Midodrine is also not effective in patients with high blood pressure or heart failure, she said.

"[Midodrine] is easy to use but kind of a pain at first," Sheldon noted. Every patient should start out taking 5 mg doses, three times a day – during waking hours. But then you have to adjust the dosage, "and it's tricky," he said.

If a patient experiences goosebumps or the sensation of worms crawling in the hair, the dose might be too much, Sheldon noted.

If the patient is still fainting, first consider when they are fainting, he said. If it's around the time they should take another dose, it might be trough effect.

Sandhu was not involved in the study, but Cedar Sinai was a participating center, and she considers Sheldon to be a mentor. Sandhu also noted that she has published papers with Sheldon, who reported no conflicts.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.


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