Gaviscon is technically an antacid, but it’s not just an antacid. It combines traditional acid-neutralizing ingredients with sodium alginate, a seaweed-derived compound that forms a physical barrier on top of your stomach contents. This dual action makes it a different product from simple antacids like Tums or Rolaids, which only neutralize acid chemically.
What Makes Gaviscon Different From a Simple Antacid
A standard antacid works by neutralizing stomach acid on contact. Calcium carbonate (the active ingredient in Tums) reacts with hydrochloric acid in your stomach and raises the pH, giving you temporary relief. The problem is that this effect is short-lived, quickly overcome by ongoing acid secretion, especially after meals.
Gaviscon contains antacid ingredients like calcium carbonate and sodium bicarbonate, so it does neutralize acid. But its defining feature is sodium alginate. When alginate meets stomach acid, it forms a gel. The sodium bicarbonate in the formula reacts with that acid to produce carbon dioxide gas, which gets trapped inside the gel. This creates a buoyant, foam-like “raft” that floats on top of your stomach contents.
That raft sits right where acid is most likely to splash up into your esophagus. In a double-blind crossover study, Gaviscon was more effective than a standard antacid (without alginate) at controlling acid exposure in the esophagus after meals. Interestingly, it didn’t reduce the number of reflux events. The same amount of liquid still splashed upward, but because the raft displaced the concentrated acid sitting at the top of the stomach, what reached the esophagus was less acidic.
How Quickly It Works
Gaviscon starts providing a noticeable cooling or soothing sensation in about 66 seconds on average. Full heartburn relief typically arrives within 3.3 minutes of a single dose. That’s comparable to the speed of standard antacids, since the acid-neutralizing ingredients begin working immediately while the alginate raft takes shape.
What’s Actually in a Dose
Gaviscon comes in several formulations that vary by country and product line. A standard chewable tablet of Gaviscon Double Action contains 250 mg of sodium alginate, 106.5 mg of sodium bicarbonate, and 187.5 mg of calcium carbonate. The liquid versions sold in the U.S. use aluminum hydroxide and magnesium carbonate as the antacid components instead of calcium carbonate.
The sodium content matters if you’re watching your salt intake. The U.S. regular-strength liquid contains 52 mg of sodium per tablespoon, while the extra-strength version contains 11 mg per teaspoon. Those amounts are modest, but they can add up across multiple daily doses, particularly for people on sodium-restricted diets or those with kidney disease.
When Gaviscon Works Better Than a Plain Antacid
The raft mechanism gives Gaviscon a specific advantage for acid reflux (GERD) rather than general stomach upset. After you eat, your stomach produces a surge of acid that pools near the top of your stomach contents, right at the junction with the esophagus. Researchers call this the “acid pocket.” A plain antacid mixes into your stomach contents and neutralizes some acid throughout, but the acid pocket can persist or reform quickly. Gaviscon’s alginate raft physically sits on that pocket, displacing or neutralizing it at the source.
If your main complaint is heartburn or acid reflux, especially after meals, Gaviscon’s barrier approach targets the problem more precisely than a simple antacid. If you’re dealing with general indigestion or a sour stomach without reflux, a plain antacid will do essentially the same job since the raft mechanism doesn’t offer much extra benefit when acid isn’t traveling upward.
Interactions With Other Medications
Because Gaviscon contains antacid compounds, it can interfere with how your body absorbs certain other medications. The NHS advises that acetaminophen (paracetamol) is safe to take at the same time, but you should check with a pharmacist before combining Gaviscon with ibuprofen or aspirin, since those painkillers can worsen acid-related symptoms on their own. As a general rule, take other medications at least two hours before or after Gaviscon to avoid absorption issues, particularly with antibiotics, thyroid medications, or iron supplements.
The Bottom Line on Classification
Gaviscon contains antacids and works partly by neutralizing acid, so calling it an antacid isn’t wrong. But labeling it as “just” an antacid misses its primary feature. Its alginate raft acts as a physical reflux barrier, which is a fundamentally different approach from what Tums or Maalox do. Pharmacologically, it’s classified as an alginate-antacid combination, and that distinction explains why it tends to outperform plain antacids for reflux symptoms while offering similar relief for basic heartburn.