What is it prescribed for?

CARDAMYST is prescribed for adults who have sudden episodes of very fast heart rate called paroxysmal supraventricular tachycardia (PSVT). These episodes often start suddenly and can cause symptoms such as palpitations, dizziness, chest discomfort, or shortness of breath.  It was approved by the FDA December 2025.

CARDAMYST is used to help restore the heart back to a normal rhythm during an active PSVT episode.

What is the name of the drug and what does it do?

The drug is called CARDAMYST™ (etripamil). It is a nasal spray that patients can use themselves when PSVT symptoms begin.

CARDAMYST works quickly to slow electrical signals in the heart and help return the heartbeat to normal.

How does it work?

CARDAMYST is a calcium channel blocker. Calcium channels help control how electrical signals travel through the heart.

By blocking these channels:

  • Electrical signals through the heart’s AV node slow down
  • Abnormal fast rhythms can stop
  • Normal sinus rhythm can be restored

Because it acts fast and is given through the nose, CARDAMYST can work within minutes.

What did the research discover?

In a large clinical study called RAPID, adults experiencing PSVT episodes used CARDAMYST at home:

  • 64% of patients returned to normal heart rhythm within 30 minutes, compared to 31% who received placebo
  • The median time to rhythm conversion was about 17 minutes with CARDAMYST versus over 50 minutes with placebo
  • Benefits were consistent across age groups, sexes, and patients taking beta blockers or other heart medications

These results showed that CARDAMYST can safely and effectively treat PSVT episodes outside of a hospital setting.

What are some of the side effects?

Most side effects are related to the nose and throat and are usually mild.

Common side effects include:

  • Nasal discomfort or burning
  • Nasal congestion or runny nose
  • Throat irritation
  • Nosebleeds

More serious but less common risks include:

  • Dizziness or fainting due to lowered blood pressure
  • Slow heart rate or heart block in people with certain heart conditions

Because of these risks, especially dizziness, CARDAMYST should be used while sitting to reduce the chance of falls.

What are the dosage recommendations and how is it prescribed?

CARDAMYST is for intranasal use only and is taken at the start of PSVT symptoms.

Recommended use:

  • First dose: One spray in each nostril (70 mg total)
  • Second dose (if needed): If symptoms continue after 10 minutes, a second 70 mg dose may be used
  • Maximum dose: Do not exceed 140 mg in 24 hours

Important instructions:

  • Stay seated for 10 minutes after use
  • Do not reuse nasal spray devices
  • Seek medical help if symptoms do not improve within 20 minutes after the second dose

CARDAMYST is not recommended for patients with certain heart conditions, such as moderate to severe heart failure or specific electrical conduction disorders.

Source:

CARDAMYST™ (etripamil) nasal spray, for intranasal use [prescribing information]. Charlotte (NC): Milestone Pharmaceuticals USA, Inc.; 2025 Dec. Accessed by: https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/218571s000lbl.pdf

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