An antacid is a substance which neutralizes stomach acidity. Antacids are bases used to neutralize the acid that causes heartburn. Despite the many commercial brand, almost all antacids act on excess stomach acid by neutralizing it with weak bases. The most common of these bases are hydroxides, carbonates, or bicarbonates. The following table contains a list of the active ingredients found in several common commercial antacids, and the reactions by which these antacids neutralize the HCl in stomach acid. The following are the main compound of antacids.

The base used as an antacid is Magnesium hydroxide.

Antacids are medications that help to neutralize stomach acid, providing relief from symptoms such as heartburn, indigestion, and acid reflux. They work by increasing the pH level in the stomach, reducing the acidity and providing a soothing effect.

Magnesium hydroxide, also known as milk of magnesia, is a common antacid that is used to treat various stomach-related issues. Let's explore why it is the base of choice for this purpose:

1. Neutralization of acid:
- Stomach acid is primarily composed of hydrochloric acid (HCl).
- Magnesium hydroxide is a strong base that reacts with the acid in the stomach, forming water and a salt.
- The chemical equation for this reaction is: Mg(OH)2 + 2HCl → MgCl2 + 2H2O.
- The formation of water helps to neutralize the excess acid, reducing its corrosive effects on the stomach lining and providing relief from symptoms.

2. Magnesium content:
- Magnesium is an essential mineral that plays a crucial role in various bodily functions.
- Magnesium hydroxide contains a significant amount of magnesium, which can help to supplement the body's magnesium levels.
- Adequate magnesium levels are important for maintaining healthy nerve and muscle function, as well as supporting bone health.

3. Safety profile:
- Magnesium hydroxide is generally considered safe for short-term use as an antacid.
- It has a low risk of side effects, although some individuals may experience diarrhea or an upset stomach.
- However, it is important to use antacids as directed and not exceed the recommended dosage, as excessive use can lead to electrolyte imbalances and other complications.

4. Availability and affordability:
- Magnesium hydroxide is readily available over-the-counter in various forms, such as tablets, suspensions, and chewable tablets.
- It is also relatively affordable compared to other antacid options, making it accessible to a wide range of individuals.

In conclusion, Magnesium hydroxide is the base used as an antacid due to its ability to neutralize stomach acid, its magnesium content, its safety profile, and its availability and affordability. However, it is always recommended to consult a healthcare professional before starting any new medication or if symptoms persist.