Skip to main content

Duo Fusion

Generic name: calcium carbonate, famotidine, and magnesium hydroxideKAL-see-um-KAR-bo-nate, fam-OH-ti-deen, mag-NEE-see-um-hye-DROX-ide ]
Brand names: Dual Action Complete, Duo Fusion, Pepcid Complete
Drug class: H2 antagonists

Medically reviewed by on Nov 6, 2023. Written by Cerner Multum.

What is Duo Fusion?

Famotidine is a histamine-2 blocker that decreases the amount of acid the stomach produces. Calcium and magnesium are naturally occurring minerals that neutralize acid in the stomach.

Duo Fusion is a combination medicine used to relieve heartburn caused by acid indigestion and sour stomach.

Duo Fusion may also be used for purposes not listed in this medication guide.

Duo Fusion side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Stop using Duo Fusion and call your doctor at once if:

Less serious side effects may be more likely, and you may have none at all.

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 FDA at 1-800-FDA-1088.


You should not use this medicine if you are allergic to famotidine or similar stomach acid reducers, such as ranitidine, cimetidine, Zantac, or Tagamet).

Do not use this medicine if you have trouble swallowing food, if you are vomiting blood, or if you have bloody or tarry stools.

Before taking this medicine

Heartburn can mimic early symptoms of a heart attack. Get emergency medical help if you have chest pain that spreads to your jaw or shoulder and you feel anxious or light-headed.

You should not use this medicine if you are allergic to famotidine or similar stomach acid reducers, such as ranitidine, cimetidine, Zantac, Tagamet, and others.

Do not use Duo Fusion if you have:

Ask a doctor or pharmacist if this medicine is safe to use if you have ever had:

This medicine may contain phenylalanine. Check the medication label if you have phenylketonuria (PKU).

Ask a doctor before using this medicine if you are pregnant or breastfeeding.

Do not give this medicine to a child younger than 12 years old without medical advice.

How should I take Duo Fusion?

Use exactly as directed on the label, or as prescribed by your doctor.

You must chew the chewable tablet before you swallow it.

Do not use more than two tablets in 24 hours.

Call your doctor if your symptoms do not improve after 14 days, or if you have ongoing stomach pain. You may have a more serious stomach condition.

In addition to taking this medication, other tips for managing heartburn include:

Store at room temperature away from moisture and heat.

What happens if I miss a dose?

Since Duo Fusion is used when needed, you may not be on a dosing schedule. Skip any missed dose if it's almost time for your next dose. Do not use two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include nausea, vomiting, diarrhea, stomach pain, fast heart rate, or fainting.

What should I avoid while taking Duo Fusion?

Do not take this medicine together with regular famotidine (Pepcid, Pepcid AC, Pepcid RPD) or with other stomach acid reducers.

Avoid foods or drinks that are more likely to cause heartburn, such as chocolate, caffeine, alcohol, some fruits and vegetables, and rich, spicy, fatty, or fried foods.

What other drugs will affect Duo Fusion?

Duo Fusion can make it harder for your body to absorb other medicines you take by mouth. Ask a doctor or pharmacist before using this medicine with any other medications.

Other drugs may affect Duo Fusion, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

More about Duo Fusion (calcium carbonate / famotidine / magnesium hydroxide)

Patient resources

Other brands

Pepcid Complete, Dual Action Complete

Professional resources

Other brands

Pepcid Complete, Dual Action Complete

Related treatment guides

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.