Why and How Antacids Work in Case of Heartburn

Heartburn is a painful burning sensation experienced in the chest area or upper stomach due to the reflux of acid in the oesophagus.

Contrary to its name, it has nothing to do with heart and is caused due to the relaxation of the lower oesophageal sphincter (LES) muscle which in turn is triggered usually by poor diet and lifestyle, though there might be other reasons possible for its malfunction.

Heartburn is a relatively common disorder and can be treated easily with mild medications and natural drugs but its negligence can lead to the development of a more severe and problematic condition called gastro oesophageal reflux disease.

Antacids and heartburn

An antacid is any substance, usually a base or a basic salt (a base or any basic chemical has high pH) which is utilised to neutralize stomach acidity (an acid has very low pH).

When the high pH antacid meets the low pH acidic conditions in the stomach, the resultant environment is neutral or of balanced pH which is neither high nor low. This reduces the efficacy of the acid and thus the harmful effects caused by excess acidity.

Mechanism of action of antacids

In our stomach, the gastric juice contains acid which helps in digesting food. The pH of the acid is 1-2 which is very low (low enough to digest zinc metal or any soft metal). Normally, the stomach lining is made of specialized cells which secrete mucous along with the gastric acid; the mucous protects the gastric lining and cells beneath the mucous from damage caused by the acids.

Due to poor diet, lack of exercise, obesity, indigestion and several other factors including some illnesses, the cells secrete more acid than the stomach can handle, which causes the mucous layer to erode.

This exposes the cells beneath the protective layer and makes them prone to damage. The damage in turn excites the nerves in the stomach which induces pain. Not just that, excessive acid exposure causes severe ulceration and inflammation in the stomach, exacerbating the effects of acidity . 

The acidity of stomach can be momentarily neutralized by antacids which are weakly basic (they have pH usually ranging from 8-10). In the reaction of acid and base, the final product formed is salt and water which increases the overall pH of the stomach from acidic to neutral (pH about 5-7).

This reduces the tendency of the acid to damage the tissues in the stomach, thus reducing pain and any other harmful effects that the acid could cause. Only weak bases are used as antacids and not strong bases (pH usually above 10) because they neutralize too much acid and become fatal .

Antacids are usually taken to treat occasional heartburns and not the frequent ones because they can only neutralize acids for a short period. If they are required frequently, a doctor should immediately be contacted as it may not just mild indigestion or heartburn and could indicate a serious problem .

There are several types of basic compounds that are be used in antacids as an active ingredient. Each product consists of one or more active ingredients with an indication of specific maximum dosage.

Each ingredient usually contributes to a minimum of 25% of acid neutralization capacity in the stomach and this may vary according to each drug governing agency in each country. Some of the common active ingredients in antacids are listed below.

Aluminium containing antacids

  • Aluminum hydroxide gel
  • Basic aluminum carbonate gel
  • Aluminum hydroxide magnesium carbonate or magnesium trisilicate codried gel
  • Dihydroxyaluminum amino acetate 
  • Aluminium phosphate gel
  • Dihydroxyaluminum sodium carbonatehow and why antacids work for heartburn

Magnesium containing antacids

  • Magnesium silicates
  • Magnesium carbonate
  • Magnesium aminosilicates
  • Magnesium hydroxides
  • Magnesium glycinate
  • Milk of magnesia dried solids

Others are:

  • Bicarbonate antacids
  • Bismuth containing antacids
  • Calcium carbonate or calcium citrate
  • Glycine
  • Phosphates containing antacids
  • Potassium containing antacids
  • Sodium containing antacids such as sodium bicarbonate and sodium potassium silicates 
  • Alginic acid containing antacids

Apart from these common bases and basic chemicals, antacids may also contain some other compounds with properties to heal other conditions in the stomach such as gas.

A typical example of such an ingredient is simethicone which is an anti-gas agent. Different types of combinations in antacids can have different effects on the stomach acidity besides neutralizing stomach acids. Antacids that contain alginic acid form a layer and float on the top of the stomach contents.

This reduces the chances of opening of the sphincter muscle, preventing the reflux of acid and thus heartburn. Simethicone containing antacids relieve pain from gas and flatulence in the stomach. Calcium containing antacids provide a supplemental source of calcium and can reduce calcium deficiency. 

Examples of common antacids 

Some common antacids are:


it is an antacids consisting of a combination of anhydrous citric acid and sodium bicarbonate, both of which are potent acid neutralizers. It is taken by dissolving 2 tablets in 4 ounces of water. For children above 12 years and adults, it can be taken by the dose of 2 tablets, every 4 hours, or as needed. The dose should never be increased beyond 8 tablets in 24 hours .


An over the counter drug, gaviscon contains aluminum hydroxide gel and magnesium carbonate which neutralize stomach acids. It also contains alginic acid which helps inhibit opening of the LES.  

It is available in the form of chewable tablets and can be taken in a dose of 2-4 tablets at a time depending on the symptoms or as indicated by the doctor. It can be taken after meals or at bedtime as needed. It should not be swallowed as a whole and should be taken with a glass of water for best results. The dose should not be exceeded more than 16 tablets in 24 hours .


This liquid drug contains a compound called bismuth salicylate which is an antacid. 1 dose of pepto bismol is measured as 2 tablespoons or 30 mL. For children above 12 years of age and adults, 1 dose can be given every ½ to 1 hour or as needed.

It should never be exceeded beyond 8 doses (16 tablespoons or 240 mL) in 24 hours. It should not be taken beyond two days. Persistence of symptoms should be informed to a doctor . 


Its contents are aluminium hydroxide, magnesium hydroxide and simethicone which together relieve acidity and gas. Another similar antacid brand with same ingredients is gelusil. The only difference is that this drug is available in the form of syrup and not tablets as gelusil.

For adults and children 12 years or older; it can be administered in a dose of 2-4 teaspoon (10-20 mL) up to 4 times a day or as needed. The dose should not be increased beyond 4 times (50-80 mL) in 24 hours . 


It is an antacid majorly available as chewable tablets. It contains calcium carbonate as its active ingredient which is also helpful as a calcium supplement for those with a calcium deficient condition. For adults and children above 12 years of age, 2-4 tablets can be chewed when the symptoms occur. The dose can be repeated a few times a day but overdose or dosage over 2 weeks should be avoided . 

Some other commonly available antacids with similar contents are Rolaids, Gelusil, Titralac, Mylanta, Alka-2 and Milk of magnesia. 

Dosage and Consumption

Antacids are usually available as over the counter drugs, which means they can be taken without prescription. Each antacid has its own dose limit and specifications which are indicated on the label. The instructions on labels should strictly be followed to avoid any discomfort or side effects.

They are available as chewable tablets, tablets to be taken with water and as syrups. Any form is equally effective but syrups usually work faster. 

An antacid should only be taken in case of occasional heartburn. If in case of regular acidity or acid reflux, more antacids are required to be consumed, the dose should never be exceeded from the one indicated on the label.

If the problem still persists, the doctor should immediately be consulted as frequent persistence of acidity symptoms might need higher medications or immediate attention due to some other disorder. An antacid is usually taken 1 hour after eating or at the time when heartburn/acidity occurs. They should never be taken with food . 

Precautions and side effects

Antacids can have a variety of side effects which can persist for a long time as well, which is why, long term and excessive usage of these drugs is not advised.

The side effects can vary depending on the contents of the antacid. Brands with magnecium may cause diarrhoea and those with aluminium may cause constipation. Some brands with calcium can also cause kidney problems .

Some common problems that excessive intake of antacids cause are depletion of some important ions or compounds in the body such as copper, phosphorus, calcium, vitamin B complex, iron, potassium, magnesium and zinc.

The deficiency of these metals and compounds can lead to severe diseases, for example, calcium and copper deficiency leads to osteoporosis, iron and vitamin B deficiency leads to anaemia, magnesium deficiency leads to heart problems, phosphorus deficiency leads to seizures, confusion and even death, and zinc depletion slows down growth

One of the most specific side effects of excessive calcium containing antacid is milk alkali syndrome, which has serious toxicity and can be fatal. It results in severe hypercalcaemia, alkalosis and renal failure .

Taking non calcium antacids for a long time can lead to increased risk of rib, hip and spine fractures along with osteoporosis . 

Antacids cannot cure more severe problems such as pain in stomach due to appendicitis, gall stones and stomach ulcers. Before taking antacids without prescription, it is important to note that a doctor or pharmacist should be considered for advice if a person is already pregnant or is suffering from renal problems, chest pain, heart disorders, blood pressure, stones or any such major disorder or is on a low sodium or high calcium diet.

This is important because the ingredients in antacids may interfere with the absorption of other drugs or may exacerbate the effects of any such disorder. 

If the antacids do not provide relief even after the consumption of maximum dose for maximum number of days/weeks indicated on the label, a doctor should be consulted immediately. Medical help should be called for in case of occurrence of bleeding, bloating, darkened bowel movements, cramping, pain, severe diarrhoea, chest pain or shortness of breath after consuming antacids . 


Antacids are very effective short term heartburn and acidity relievers. They can be taken without a prescription and are not harmful to the body if taken with full precautions; however, long term and excessive use of antacids is strictly unadvisable.

Though they are generally safe to consume but their exploitation can be deleterious to health and thus they are suitable only for occasional heartburns and not for severe gastro-oesophageal reflux disease.