What is the immediate action of over-the-counter antacids for older children experiencing heartburn?

Neutralizing the acid already present in the stomach.

For older children who experience acute, short-term relief needs for heartburn associated with GERD, over-the-counter antacids are often the initial medical suggestion. Antacids function as bases, and their mechanism of action is purely chemical: they directly interact with and neutralize the hydrochloric acid that is already present within the stomach cavity. This immediate acid neutralization provides rapid symptomatic relief from the burning sensation. This contrasts significantly with medications like H2 blockers or Proton Pump Inhibitors (PPIs), which work by interfering with the physiological processes designed to decrease the *production* or secretion of acid over a longer duration.