Does an antacid reduce or increase aspirin absorption?
Antacids can reduce aspirin absorption. Aspirin (acetylsalicylic acid) is absorbed differently depending on stomach acidity, and making the stomach less acidic (one of antacid’s main effects) can lower how much aspirin dissolves and is absorbed in the upper gastrointestinal tract.
What happens if the antacid changes stomach acid?
Many antacids work by neutralizing stomach acid. Because aspirin’s absorption is affected by pH, raising stomach pH typically reduces the fraction of aspirin in a form that dissolves/absorbs well in the stomach/early small intestine. That means taking an antacid at the same time may reduce aspirin absorption.
Does the timing matter (right together vs. hours apart)?
Yes. If antacid and aspirin are taken close together, the pH change can interfere more with aspirin absorption. Separating doses by several hours can lessen this effect, but exact timing guidance depends on the specific antacid and aspirin regimen.
What about “buffered” aspirin or enteric-coated aspirin?
Some aspirin products are formulated to delay or modify absorption (for example, enteric-coated or buffered formulations). These formulations change how and where aspirin is absorbed, so the interaction with antacids can be less straightforward than with standard immediate-release aspirin.
Are there safety reasons to avoid mixing?
A common reason people take both is symptom relief (heartburn/indigestion), but aspirin can irritate the stomach lining and increase bleeding risk. If an antacid is being used to manage aspirin-related stomach upset, it’s still important to discuss the plan with a clinician, especially for regular dosing (for example, low-dose aspirin for cardiovascular prevention).
Can you tell which antacid you mean?
Different antacids (calcium carbonate, magnesium hydroxide, aluminum hydroxide, etc.) can have different effects. If you share the antacid name and whether your aspirin is regular, buffered, or enteric-coated (and the dose), I can give a more specific answer about the interaction direction and practical spacing.