Hydroxide, most commonly in the form of magnesium hydroxide or aluminum hydroxide, is widely used as an antacid to treat overacidity (gastric hyperacidity or heartburn). The scientific rationale for its use is well-established: hydroxide ions (OH⁻) are basic and react with excess hydrochloric acid (HCl) in the stomach to form water and the corresponding salt (for example, MgCl₂ or AlCl₃). This neutralization reaction reduces gastric acidity, providing symptomatic relief from discomfort due to excess stomach acid.

Numerous clinical studies and pharmacological reviews support the efficacy and safety of hydroxide-based antacids. For instance, magnesium hydroxide ("milk of magnesia") and aluminum hydroxide are both listed as over-the-counter medications for the symptomatic relief of heartburn, indigestion, and acid reflux by regulatory agencies such as the FDA and EMA. Their mechanism of action, dosing, and expected side effects are well-characterized in standard pharmacology texts and treatment guidelines.

While long-term or excessive use can cause side effects (such as diarrhea with magnesium salts or constipation with aluminum salts), their acute use for overacidity is both scientifically validated and widely recommended in clinical practice. In summary, the use of hydroxide to treat overacidity is firmly rooted in scientific evidence.