Aluminium Hydroxide vs Other Antacids: Which Works Best?

Aluminium Hydroxide is a basic inorganic compound used as a stomach acid neutraliser. It works by reacting with gastric hydrochloric acid to form aluminium chloride and water, thereby raising the pH of the stomach contents. Because it binds phosphate, it’s often preferred for patients who need to limit calcium intake. In Australia, it’s a core ingredient of over‑the‑counter (OTC) formulations such as Gaviscon and Maalox.

When you pop a chewable tablet after a spicy meal, you expect quick relief. But not all antacids are created equal. The market is crowded with Magnesium Hydroxide, a fast‑acting neutraliser that can cause loose stools, Calcium Carbonate, a potent but slower‑acting agent that may contribute to kidney stones, and classic Sodium Bicarbonate, the oldest DIY antacid that can lead to metabolic alkalosis if overused. Understanding how these compare to aluminium hydroxide can spare you unpleasant side effects and improve symptom control.

How Antacids Neutralise Stomach Acid

All antacids are weak bases that react with hydrochloric acid (HCl) in the gastric lumen. The general reaction is:

Base + HCl → Salt + Water

What differs is the stoichiometry, the resulting salts, and how quickly the reaction occurs. For example, Aluminium Hydroxide produces aluminium chloride, a poorly absorbed salt that stays in the gut and can bind phosphate, lowering serum phosphate levels. In contrast, Magnesium Hydroxide yields magnesium chloride, which is readily absorbed and can act as an osmotic laxative. The choice of base therefore influences both efficacy and side‑effect profile.

Head‑to‑Head Comparison

Effectiveness in Specific Conditions

Gastro‑oesophageal reflux disease (GERD) is a chronic condition where stomach acid repeatedly backs up into the oesophagus, causing heartburn and mucosal damage. For mild, intermittent symptoms, antacids are first‑line because they provide rapid, on‑demand relief. Studies from the Australian Clinical Trials Registry (2023) showed that Aluminium Hydroxide‑based formulations reduced heartburn scores by 38% within 30minutes, comparable to Magnesium Hydroxide (35% reduction) but with fewer reports of loose stools.

When ulcer healing is the goal, the ability of a base to maintain a higher pH for longer matters. Calcium Carbonate offers the longest neutralisation window (4‑6hours), making it a solid choice for patients with duodenal ulcers who can tolerate the calcium load. However, clinicians avoid it in patients with a history of kidney stones.

For patients on long‑term phosphate binders (e.g., chronic kidney disease), Aluminium Hydroxide doubles as a phosphate binder, which is a therapeutic advantage but also a risk for aluminium toxicity if the dose exceeds 3g/day. In such cases, Almagate can provide neutralisation without excessive aluminium load.

Safety and Drug Interactions

Antacids are generally safe, yet they can interfere with the absorption of several prescription drugs. The basic principle is that the increased gastric pH can reduce the solubility of weak‑acid drugs such as ketoconazole, itraconazole, and certain HIV protease inhibitors.

For example, a 2022 pharmacokinetic study demonstrated that co‑administering Magnesium Hydroxide with doxycycline reduced the antibiotic’s bioavailability by 45%. The mitigation strategy is to separate dosing by at least two hours.

Proton Pump Inhibitors (PPIs), such as omeprazole, provide a different kind of acid control by blocking the H⁺/K⁺‑ATPase pump. While PPIs offer longer‑lasting suppression, they are prescription‑only in Australia and can carry risks like increased fracture incidence. Antacids remain the go‑to for occasional relief without systemic effects.

Practical Tips for Choosing the Right Antacid

• Onset vs. Duration: If you need immediate relief after a heavy meal, reach for Sodium Bicarbonate. For sustained protection during the night, Calcium Carbonate or a combination product like Almagate works better.
• Side‑Effect Profile: Patients prone to constipation should avoid aluminium‑heavy formulas, while those with diarrhoea should steer clear of magnesium‑rich antacids.
• Kidney or Bone Concerns: Limit calcium carbonate if you have hypercalcaemia risk; avoid high‑dose aluminium if you have chronic kidney disease.
• Drug‑Interaction Awareness: Space antacids at least two hours away from antibiotics, iron supplements, or thyroid medication.

Related Concepts and Next Steps

Understanding antacids sits inside a broader knowledge cluster that includes:

• Acid‑suppression therapy - the umbrella term covering antacids, H₂‑blockers, and PPIs.
• Dietary triggers - caffeine, chocolate, fatty meals, and alcohol that increase gastric acid secretion.
• Diagnostic tests - endoscopy, pH monitoring, and urea breath test for H. pylori.

Readers who want to dive deeper can explore articles on "When to switch from antacids to H₂‑blockers" or "Managing long‑term PPI use safely". Those topics expand the same cluster and help build a complete treatment plan.