Maalox is an over-the-counter antacid used to relieve heartburn, acid indigestion, sour stomach, and gas. It works by neutralizing stomach acid on contact, which is why it’s considered a fast-acting option for digestive discomfort. The liquid formula contains three active ingredients: aluminum hydroxide, magnesium hydroxide, and simethicone.
What Maalox Treats
Maalox is labeled for five specific symptoms: acid indigestion, heartburn, sour stomach, upset stomach associated with those conditions, and the pressure and bloating commonly referred to as gas. The first three are all caused by excess stomach acid irritating your esophagus or stomach lining. The gas-related relief comes from simethicone, which breaks up gas bubbles in your digestive tract so they’re easier to pass.
This makes Maalox a two-in-one product. Most plain antacids only neutralize acid. Maalox handles both the acid problem and the bloating that often comes with it.
How the Ingredients Work Together
Aluminum hydroxide and magnesium hydroxide are both mineral salts that react directly with hydrochloric acid in your stomach, converting it into water and neutral salts. Relief typically starts within minutes of taking a dose because the reaction happens on contact rather than needing to be absorbed into your bloodstream.
The two minerals are paired deliberately. Aluminum hydroxide tends to cause constipation, while magnesium hydroxide tends to cause loose stools. Combined, they largely cancel out each other’s digestive side effects. Simethicone, the third ingredient, is not an antacid at all. It’s an anti-foaming agent that collapses gas bubbles so your body can eliminate them more easily.
Dosing Limits
Adults and children 12 and older can take 2 to 4 teaspoons (10 to 20 mL) of the liquid up to four times a day. The maximum in any 24-hour period is 16 teaspoons (80 mL), and you shouldn’t use the maximum dose for longer than two weeks without medical guidance. If you’re still dealing with symptoms after two weeks of regular use, something beyond occasional acid irritation may be going on.
Side Effects
Side effects from Maalox are uncommon at normal doses. The most frequently reported ones are diarrhea and constipation, reflecting the push-pull of the magnesium and aluminum components. Some people also notice loss of appetite, unusual tiredness, or muscle weakness, though these are rare with short-term use. The chalky taste bothers some people. Taking it with water or milk helps.
Who Should Be Cautious
The biggest safety concern involves kidney function. Your kidneys are responsible for clearing excess magnesium from your body. When kidney function is reduced, magnesium from antacids like Maalox can accumulate in the blood, a condition called hypermagnesemia. People with end-stage kidney disease often already have mildly elevated magnesium levels, and magnesium-containing antacids can push those levels higher.
A study of 320 hospitalized patients who developed elevated magnesium identified four independent risk factors: reduced kidney filtration rate, elevated markers of kidney stress, higher antacid doses, and use lasting longer than about five weeks. If you have any degree of kidney disease, this is a product to discuss with your doctor before using regularly.
Safety During Pregnancy and Breastfeeding
Antacids containing aluminum hydroxide and magnesium hydroxide are considered first-line options for heartburn during breastfeeding. Both minerals have poor oral bioavailability, meaning very little gets absorbed into the bloodstream in the first place, so the amount that could reach breast milk is minimal. Aluminum and magnesium are both naturally present in breast milk, and no side effects in breastfed infants have been reported. No specific infant monitoring is usually required.
Heartburn is extremely common during pregnancy as well, and aluminum/magnesium antacids have a long track record of use. That said, the simethicone component and overall dosing are worth confirming with your provider during pregnancy, since recommendations can vary.
Interactions With Other Medications
Maalox can interfere with how your body absorbs certain medications, particularly antibiotics. The aluminum and magnesium ions bind to some drugs in your stomach, preventing them from being fully absorbed. One study found that taking a common antibiotic at the same time as Maalox reduced the drug’s absorption by 59%. Separating the doses by several hours largely eliminated the problem.
This interaction applies broadly to medications that bind with minerals. If you take any prescription drugs regularly, the safest approach is to take Maalox at least two hours before or after your other medications.
How Maalox Compares to Other Antacids
The main alternative you’ll see on the shelf is a calcium-based antacid like Tums or Rolaids. Both types neutralize acid, but they differ in a few practical ways. Magnesium-based antacids like Maalox are generally considered faster-acting. Calcium-based antacids have the added benefit of providing supplemental calcium, which some people prefer for that reason alone.
Maalox comes as a liquid, which coats the stomach lining more evenly than a chewable tablet. This can matter if your discomfort is spread across your upper abdomen rather than concentrated in one spot. On the other hand, tablets are far more portable. The choice often comes down to convenience and personal preference, since both types are effective for the same set of symptoms.
Neither type is designed for long-term acid suppression. If you find yourself reaching for any antacid daily for weeks at a time, that’s a signal to look into longer-acting options like H2 blockers or proton pump inhibitors, which reduce acid production rather than just neutralizing what’s already there.