New FDA-Approved Nasal Spray Aims to Let PSVT Patients Treat Rapid Heart Rhythm at Home

On a recent night in Charlotte, a woman in her 50s felt a familiar jolt in her chest: her heart suddenly racing past 180 beats a minute, breath shortening, hands trembling. In the past, it would have meant a rushed trip to the emergency room, an intravenous line and a brief but jarring dose of adenosine to shock her rhythm back to normal.

Starting this week, for many of the more than 2 million Americans with the same heart rhythm problem, it could instead mean sitting down, taking out a small device and spraying medicine into each nostril.

Milestone Pharmaceuticals said Monday that its drug CARDAMYST, a nasal spray version of the calcium channel blocker etripamil, is now on shelves at retail pharmacies across the United States. The medicine, approved by the Food and Drug Administration on Dec. 12, 2025, is cleared “for the conversion of acute symptomatic episodes of paroxysmal supraventricular tachycardia (PSVT) to sinus rhythm in adults.”

The company calls it the first and only FDA-approved, self-administered treatment for PSVT episodes and the first FDA-approved therapy for the condition in more than 30 years.

“With the U.S. launch of CARDAMYST, patients now have a convenient, self-administered option designed to treat episodes of PSVT wherever and whenever they occur,” Milestone President and Chief Executive Joseph Oliveto said in the company’s announcement.

What PSVT is—and why it often sends patients to the ER

PSVT is a group of arrhythmias in which an electrical short circuit above the heart’s ventricles sends the pulse suddenly soaring, often to 150 to 200 beats per minute. Episodes can last minutes to hours and are typically characterized by palpitations, chest discomfort, shortness of breath, anxiety, lightheadedness or, in some cases, fainting.

The condition is not rare. Large insurance-claims studies estimate that more than 1.2 million U.S. adults have PSVT as a primary rhythm disorder, and more than 2 million when patients with overlapping atrial fibrillation or flutter are included. The burden falls disproportionately on older adults and women.

For decades, treatment has followed a narrow path. Patients are taught so-called vagal maneuvers—breathing or positional techniques that increase vagal tone and can break certain arrhythmias. If that fails or symptoms are severe, the next stop is usually the emergency department, where clinicians give a rapid IV push of adenosine or use intravenous beta-blockers or calcium channel blockers under monitoring. Many patients eventually undergo catheter ablation, an invasive but often curative procedure that uses catheters threaded into the heart to destroy the short-circuit pathway.

“Historically, PSVT has meant repeated ER visits or a trip to the electrophysiology lab for ablation,” said one academic electrophysiologist who has studied the condition. “We haven’t had an on-demand medication that patients could reliably use on their own.”

How CARDAMYST works

Etripamil is designed to fill that gap. The drug is a short-acting, non-dihydropyridine L-type calcium channel blocker, pharmacologically related to verapamil but formulated as an intranasal spray. The nasal route allows rapid absorption into the bloodstream and fast onset of action, while its brief duration is meant to reduce the risk of prolonged low blood pressure or slow heart rate.

Under the prescribing information, adults with a confirmed diagnosis of PSVT are instructed to use one single-use device—two sprays, one into each nostril—at the onset of an episode. If symptoms persist after 10 minutes, they may use a second device in the same way. The maximum recommended total dose is 140 milligrams in 24 hours.

What the clinical trials found

The FDA’s approval was based on a multi-study clinical program that enrolled more than 1,800 participants and captured more than 2,000 treated PSVT episodes. In the pivotal Phase 3 RAPID trial, adults with documented PSVT were randomized to receive self-administered etripamil nasal spray or placebo when they experienced an attack outside a hospital.

Within 30 minutes of dosing, 64% of etripamil-treated patients had converted back to normal sinus rhythm, compared with 31% in the placebo group, investigators reported. The median time to conversion was 17 minutes on the drug, versus 54 minutes on placebo. By one hour, about 73% of patients who took etripamil had converted.

Supportive data from an open-label extension study, in which patients used etripamil repeatedly over many months, showed similar performance, with a median time to conversion of roughly 15 minutes and no new cardiac safety issues reported in the 24 hours after dosing.

A pooled analysis of two Phase 3 trials found that patients who used etripamil were also less likely to end up seeking emergency care. About 13.6% of those receiving the drug went to the emergency department after a treated episode, compared with 22.4% of those assigned to placebo—corresponding to a relative reduction of about 39%. Investigators noted that vagal maneuvers, which nearly all participants attempted before using the spray, terminated their episodes without further treatment in fewer than 5% of cases.

Safety, contraindications, and patient instructions

Side effects in the trials were mostly mild and related to the nose and throat, such as congestion, discomfort, runny nose and minor nosebleeds. The FDA-approved label carries warnings about possible drops in blood pressure, slowed heart rate and fainting, and lists several contraindications, including moderate to severe heart failure, certain conduction system diseases and specific pre-excitation syndromes such as Wolff-Parkinson-White.

Patients are advised to administer the spray while seated, in a safe place, and to lie down if they feel dizzy or lightheaded. Physicians are expected to confirm the diagnosis of PSVT, review contraindications and provide a clear action plan before prescribing the drug.

Cost pressures—and Milestone’s access plans

The launch of CARDAMYST comes against a backdrop of rising attention to the cost of arrhythmia care. Analyses of large employer and Medicare claims databases show that annual healthcare spending for patients newly diagnosed with PSVT more than doubles in the year after diagnosis and remains elevated for years, driven by emergency visits, hospitalizations, diagnostic testing and procedures.

Milestone has cited outside estimates that PSVT accounts each year in the United States for roughly 140,000 to 525,000 emergency department visits, 40,000 to 120,000 inpatient hospitalizations and around 100,000 catheter ablations, with total spending on management approaching $5 billion annually.

In a budget-impact model commissioned by the company, health economists projected that adding etripamil to a commercial health plan’s formulary, with modest uptake over three years, would reduce inpatient admissions, emergency visits and outpatient hospital visits related to PSVT, as well as the number of ablation procedures. The model found that, after accounting for lower acute-care spending, the net added cost of the drug would be only a few cents per member per month.

Milestone is rolling out CARDAMYST with a patient support hub aimed at smoothing access and copays. For patients with commercial insurance who meet eligibility criteria, the company said out-of-pocket costs are expected to be capped at $25. The announcement did not specify pricing for Medicare, Medicaid or uninsured patients.

Regulatory hurdles and what comes next

The company’s path to market was not without setbacks. The FDA initially issued a refusal-to-file letter in 2023, citing technical issues with the structure of Milestone’s data submission. After resubmission, the agency sent a complete response letter in March 2025 focused on chemistry and manufacturing controls and questions around nitrosamine impurities, a class of contaminants that has prompted closer scrutiny across multiple drug products in recent years. Regulators did not request additional clinical trials, and the drug was approved after the company addressed the manufacturing concerns.

For clinicians, the arrival of an at-home option raises both opportunities and new decisions.

“This gives appropriately selected patients more control and could reduce unnecessary emergency visits, which is appealing,” the electrophysiologist said. “At the same time, we’ll need to be very clear about who should not use it and when symptoms should prompt a 911 call instead of a spray.”

Professional guidelines on supraventricular tachycardia from the American College of Cardiology, American Heart Association and Heart Rhythm Society were last updated in 2015, before etripamil was developed. Experts expect future revisions to weigh where, and for which patients, a self-administered nasal spray should sit alongside long-standing recommendations for vagal maneuvers, intravenous drugs and catheter ablation.

Milestone, a small cardiovascular-focused drugmaker with operations in Montreal and Charlotte, N.C., is betting that acceptance in PSVT will open the door to broader use of etripamil in other rhythm problems. The company is planning late-stage trials in adults with atrial fibrillation and rapid ventricular response, a far more common condition that also frequently drives emergency visits.

Across the healthcare system, the broader question is whether CARDAMYST marks the start of a new category: acute cardiac treatments delivered not in hospital bays, but in living rooms, offices and airplanes.

For the Charlotte patient with PSVT, that could mean something simpler. Instead of rehearsing the route to the emergency department, she may soon need to remember just two quick sprays and a place to sit while her heart slows back down.