Cardamyst

Cardamyst is a prescription nasal spray used for acute paroxysmal supraventricular tachycardia (PSVT) to restore normal heart rhythm.

Cardamyst nasal spray can be self-administered when needed to quickly stop PSVT episodes and reduce the need for medical care.

Cardamyst works by reducing calcium entry in AV nodal cells, slowing conduction, and interrupting the reentry circuit that causes PSVT, helping restore normal sinus rhythm. Cardamyst (etripamil) is a calcium channel blocker.

Cardamyst FDA approval was granted for the conversion of acute symptomatic episodes of paroxysmal supraventricular tachycardia to sinus rhythm in adults, on December 12, 2025.

In the Phase 3 RAPID trial, 64% of participants who self-administered Cardamyst converted from SVT to normal sinus rhythm within 30 minutes, compared with 31% on placebo (HR 2.62; p<0.001). By one hour, 73% had converted, and Cardamyst shortened the median time to conversion to 17 minutes versus 54 minutes with placebo.

Do not use Caramyst if:

• are allergic to etripamil or to any of its inactive ingredients. See the end of this page for a complete list of ingredients in this nasal spray
• have limitations in activities due to heart failure (moderate to severe heart failure)
• have Wolff-Parkinson-White (WPW) syndrome, Lown-Ganong-Levine (LGL) syndrome, or an abnormal heart rhythm pattern called pre-excitation (delta wave) on an electrocardiogram (ECG)
• have sick sinus syndrome without a permanent pacemaker
• have a second degree or higher atrioventricular (AV) block.

Before using Cardamyst tell your healthcare provider about all of your medical conditions, including if you:

• have a history of fainting
• have low blood pressure.

Pregnancy

Tell your healthcare professional is you are pregnant or plan to become pregnant. It is not known if Cardamyst will harm your unborn baby.

Breastfeeding

Tell your healthcare professional are breastfeeding or plan to breastfeed. It is not known if Cardamyst passes into your breast milk. You should stop breastfeeding for 12 hours after treatment with Cardamyst. During this time, pump and throw away your breast milk. Talk to your healthcare provider about the best way to feed your baby after using this medicine.

The most common Cardamyst side effects include:

• nasal discomfort
• nasal congestion
• runny nose
• throat irritation
• nosebleed

Serious side effects

Fainting due to the effects on blood pressure, heart rate, and electrical activity of the heart. This medicine may cause dizziness and fainting, especially in people with a history of fainting and certain heart problems, or people with a history of fainting during an episode of PVST.

Use Cardamyst while sitting in a safe area where you will not fall if you become dizzy or lightheaded. Lie down if you feel dizzy or lightheaded after using this medicine. If fainting occurs after using this nasal spray, caregivers should place you on your back and seek medical help.

These are not all of the possible side effects of Cardamyst.

Call your doctor for medical advice about side effects. This is not a complete list of side effects, and others may occur. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088

Cardamyst is a nasal spray that is sprayed into the nostrils as soon as possible after your PSVT symptoms begin.

Cardamyst Dose

• One spray in each nostril (total 70 mg).
• If symptoms persist after 10 minutes: use a second device for another 70 mg (again one spray per nostril)
• Maximum: 140 mg in 24 hours (no more than 2 devices)

Cardamyst instructions

Step 1

Remove the device from the carrying case:

• Each carrying case contains 2 Cardamyst devices.
• Each Cardamyst device contains 1 dose consisting of 2 sprays (1 spray for each nostril).
• Open the lid and carefully remove 1 nasal spray device from the carrying case.

Step 2

Sit down and hold the nasal spray device in your hand:

• Hold the Cardamyst device in an upright position with your thumb on the bottom of the plunger and the tip between your index and middle fingers.
• Do not press the plunger yet.

Step 3

Insert the nasal spray device into the first nostril and spray:

• Keep your head straight.
• Insert the tip of the nasal spray device into 1 nostril until your index and middle finger are touching the bottom of your nose.
• Using your thumb, press the plunger firmly and quickly all the way up.
• Breathe normally. Avoid inhaling deeply

Step 4

Release the plunger:

• Completely release the plunger.
• Remove the nasal spray device from the first nostril.

Step 5

Insert the same nasal spray device into the second nostril and spray right away:

• With the same nasal spray device, repeat Steps 3 and 4 in the second nostril right away.
• Breathe normally. Avoid inhaling deeply.

Step 6

Stay seated and keep your head straight for 10 minutes:

• For Cardamyst to work right away, keep your head straight for 10 minutes, as shown.
• When medicine drips out, wipe your nose.
• Do not blow your nose for 10 minutes.
• Throw away (discard) the Cardamyst device after use.

Step 7

If you continue to have symptoms after 10 minutes:

Repeat Steps 1 to 6 with a new device.

If your symptoms have not improved within 20 minutes after your second dose, call your healthcare provider or get emergency medical help right away.

Do not use more than 2 Cardamyst devices (140 mg) within a 24-hour period.

Replace the used Cardamyst device with a new one right after use, so you will have a new nasal spray device in case you need it.

Other drugs may interact with Cardamyst, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here

Store device at room temperature between 20°C to 25°C (68°F to 77°F).

Keep out of the reach of children.

Active ingredient: etripamil

Inactive ingredients: acetic acid, edetate disodium, sulfuric acid, and water for injection.

Manufactured for: Milestone Pharmaceuticals USA, Inc., 6210 Ardrey Kell Road, Suite 650, Charlotte, NC, 28277