What Is Aluminum Hydroxide/Magnesium Hydroxide? Uses, Dosage, and What You Need to Know in 2026

Aluminum hydroxide and magnesium hydroxide — two words you've probably seen on the back of antacid bottles — are among the most widely used OTC active ingredients in the world. Whether you know them as Mylanta, a hospital antacid, or simply "the antacid," these two compounds work together to quickly neutralize stomach acid and relieve heartburn, indigestion, and stomach upset.

This guide covers everything you need to know about this combination antacid in 2026: what it is, what it treats, how to use it correctly, who should be cautious, and when to consider something stronger.

What Is Aluminum Hydroxide/Magnesium Hydroxide?

Aluminum hydroxide and magnesium hydroxide are two separate antacid compounds that are frequently combined in a single product. Each is an alkaline substance that neutralizes hydrochloric acid (HCl) in the stomach. When combined, they complement each other: aluminum hydroxide acts more slowly but has a longer duration, while magnesium hydroxide works more quickly but wears off faster.

Both compounds are FDA-approved for OTC antacid use and are classified as antacid drug products. They are not controlled substances. The British Pharmacopoeia recognizes the combination under the name "co-magaldrox."

What Brand Names Contain These Active Ingredients?

The most well-known brand in the U.S. is Mylanta, specifically Mylanta Maximum Strength (which also includes simethicone for gas). The brand-name Maalox was discontinued in the U.S. market but was historically a major product with these same active ingredients. Today, numerous store brands at CVS, Walgreens, Walmart, and other retailers carry generic versions with the same formulation.

What Conditions Does It Treat?

Aluminum hydroxide/magnesium hydroxide is used to relieve:

• Heartburn: The burning sensation in the chest caused by stomach acid backing up into the esophagus
• Acid indigestion: Discomfort or burning in the stomach caused by too much acid, often after eating
• Sour stomach: A feeling of acid accumulation in the stomach
• Upset stomach: General discomfort associated with too much stomach acid
• Symptomatic relief in peptic ulcer, gastritis, esophagitis, and hiatal hernia: When used as an adjunct under physician supervision

What Dosage Forms Are Available?

Aluminum hydroxide/magnesium hydroxide is available in:

• Oral liquid suspension: Regular strength (200mg/200mg per 5mL) and Maximum strength (400mg/400mg per 5mL). Shake well before use.
• Chewable tablets: Must be chewed thoroughly before swallowing; do not swallow whole.
• Unit-dose cups: Used primarily in hospital and long-term care settings.

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How Do You Take It Correctly?

For adults and children 12 and older:

• Liquid: Take 10-20 mL (2-4 teaspoons) 4 times daily between meals and at bedtime as needed
• Do not exceed 60-80 mL in 24 hours (check your specific product label for exact maximum)
• Do not use for more than 2 weeks continuously without physician guidance
• Separate from other medications by at least 2 hours (4 hours for levothyroxine)
• Shake liquid suspension well before each use

Who Should Not Use This Antacid?

Avoid or use with caution if you:

• Have kidney disease (risk of magnesium and aluminum accumulation)
• Have intestinal obstruction
• Are allergic to aluminum or magnesium compounds
• Are pregnant (aluminum hydroxide is not recommended; consult your OB-GYN)
• Are under 12 years old (do not give to children under 12 without medical advice)

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Finding Aluminum Hydroxide/Magnesium Hydroxide Near You

This antacid is widely available OTC, but specific formulations or brands may not be at every pharmacy. medfinder calls pharmacies near you to check which ones have your medication in stock and texts you the results. To understand more about how this drug works, read our guide on how aluminum hydroxide/magnesium hydroxide works.